Wayne, way back when Leica first shipped their digital back add-on for the R system, what they called the DMR, I coined the phrase "Slippery Slope" to describe the very process you are now following to others that at that time were asking about lenses for their Leica "R" cameras. People who have come before you, as I and most of us here have, will likely laugh with understanding at the term "Slippery Slope." We've already slid down it! :ROTFL:
So here let me add to what advice you've already been given in the post above. The multi-focal lenses are all excellent quality and tack sharp, but they are slow. Think f/4 slow wide open, and what that means to your sinking shutter speed in low light. For landscape use you'd likely be on a tripod so that won't bother you as much as it would myself as a people shooter. These combo lenses are not cheap, however. Slow and Expensive.
I've shot most everything now that Leica has ever made for an M body, save for the new 24 'Lux, which I expect is spectacular. Since you asked for a recommendation about my favorites, I will not take price as an obstacle in considering and will instead offer up my opinion as to what would be the top performer within your focal range. Please understand though that overall, you will not find a better assortment of quality lenses for another 35mm camera. All other systems have positive DOGS in their lens lineup, and focal coverage holes in the available choices. Leica is the exception.
The M system has been made for more years than most of us have been alive, so there is an enormous quantity of lens choices available that will fit on your M9. The latest ASPH designs at all speeds and focal lengths are outstanding, and very consistent across the lineup in color and look, save for the Summilux versions and the Noctilux which have a completely different drawing signature and Boke. Lenses manufactured before the 1950's have coatings for B&W photographic film, so will behave in unusual ways in some cases when used with your M9 digital sensor. I happen to enjoy this more artistic rendering myself, but many people prefer everything tack sharp. The "Leica Glow" as often described is very evident in most of the older glass, particularly in the 35mm & 50mm focal lengths. There are many fine lenses to be found in this group, and at prices far below what you will end up paying for new lenses. Are they as good? Depends completely upon how you define the word.
To fully understand the Leica lens choices and their differences, you must first understand the Leica Philosophy that guided their design in the first place. Leica in many ways is a throwback to days long departed for most companies still in business today. Their whole point in being is to build the very best optic possible with the latest design technology available at the time. This is the way it was done when the company was founded, and this is the way it has always been done every day since. Looked at simply from an R&D perspective, this makes things very simple. When a lens can be improved upon sufficiently to make a detectable image quality difference, a new design project is launched. When completed, along with the many other pieces that go into it such as the manufacturing, quality control inspection steps, production parts procurement, and the all important training for the line assembly and manufacturing staff, the new lens is put into production.
For a company of low production volume such as Leica, this takes years. So while all of the later Leica generations of a lens are going to be superior in viewing the final image when looked at as a lens designer. But let's not forget that what these designers start with is the design books of their predecessors, who were also the very top lens designers of their own generation, and who carefully followed the tradition of passing along all of their own design notes, research, and help full hints on what has and has not worked in the past. This "Institutional Memory" as business analysts call it, is the huge advantage the present Leica Chief Lens Engineer starts out with. Every new lens change advances the design and manufacturing art another step, in an ever continuing chain.
Since the day the first Leica M optic was made, they have enjoyed the reputation of the finest available in the 35mm focal length. Since day one. How does that impact you? Very simply. Every old lens made by Leica for the M camera you buy today was, the day it was manufactured, the finest available in it's focal length and speed at the time. So every "old" Leica lens is pretty dang good when you come right down to it. Sure, some are better at some things than others, but across the board I do not believe you can buy a "poor" Leica M lens, they never made any!
Though you can easily buy a poor copy of one. Lenses are mechanical in design, so do have moving parts. Older lenses were made at a time before modern lubricants were available. Leica recommends that all lenses be periodically examined, cleaned, lubricated, and re-adjusted to bring it into exact tolerances. Or CLA, as you will often see it referred to. This is an important consideration when purchasing particularly a lens twenty years old or more. It likely will need a CLA before functioning to build standards. This too will require an additional investment over and above the cost of the used lens.
Please note I use the word investment instead of expense too. While there is no question the cost of a new Leica lens is very high. It has to be. There is no way humanly possible to hand make, hand polish the glass elements, and hand fit assemble an optic of this quality built to these exacting mechanical precision standards out of some of the most expensive rare earth elements on the planet, and not have it cost a small fortune. They invest a small fortune making them this way! But I, for one, along with most every other Leica owner hope they never stop this practice. This practice alone is the real value of your investment long term. As labor and rare materials costs rise, so do the prices of new lenses. Every time a politician here in the USA causes the dollar to rise, so do the prices on new Leica lenses. As long as Leica still follows this well stated Leica Policy of continued improvement, the value of every existing Leica lens will continue to rise. It is simple economics. In all the years I have bought Leica M lenses, I have never regretted buying a single one. They've all been a true delight for me, the oldest to the newest, and they all let an artist do their thing :thumbs:
The best wide angle 21mm lens I have ever seen in ANY mount for 35mm cameras is the outstanding Leica 21mm f/1.4 Summilux ASPH. It's dearly expensive, $6,500 but worth every penny of it and much more. For landscape or people use, you will never find a better wide in my opinion. I own one of these myself, and it is my primary lens that lives most of the time on my M9 body.
The 24 f/1.4 Summilux should likewise be of similar nature to the 21mm sister. They both derive from the same design. The 24mm f/2.8 Elmarit ASPH I also own, and find it too to be an excellent choice for a landscape use, particularly because of it's excellent micro contrast that helps resolve all those landscape small details. The 28mm 'Cron ASPH is certainly not to be overlooked, another fantastic lens I own and use often when 21mm is just too wide. If you positively must have speed, the 35 & 50 'Lux are both good but in my opinion quality wise I believe the f/2 'Cron versions are technically superior particularly for landscape use where the higher micro and macro contrast of the 'Cron gives them a visual landscape advantage. The f/2 'Cron versions of both are also substantially less costly, and take up a fraction of the room and weight allowance as they are both smaller and lighter to carry in the field.
Sorry to write a book here, but my opinions sometimes take a bit of space to express. Bottom line, if you can, avoid the "Slippery Slope" and either save your money and quit right now, or plan that you too will start to experience "lens creep," that evil disease that seems to erode all of the available space on your credit cards over time. Once you start using that M9, there is no return if you are comfortable with shooting a rangefinder. Nothing else will ever do the same as it does, and nothing else will ever work the same as it does. For we nerd wing nuts who have used it so long, there is no other camera made we would rather use. You see, shooting any M is like shooting an old friend and partner in photography, not some technical contraption. Be forewarned, it will also drain your credit card navigating the "Slippery Slope" of M lens choices :salute:
Best of luck, welcome to the M owners club, and enjoy your new purchase!