Hi Wayne, I own both the 23 and the 40. I have shot with the 28 but don't own one. I won't steer you one way or the other - that's your call, but I will share some of the considerations that played on my mind at the time.
The question of angle of view is obviously one only you can decide for yourself. I can't remember which back you shoot with (forgive me!), but the number of pixels you bring to the game has some bearing on the issue. I shoot with the IQ180, so I have the luxury of cropping when I need to. This was a consideration in choosing the 23 over the 28 and 32. Basically, I chose the widest lens available at the time, knowing I could crop if I needed to. You can't make an image from a 28 or 32 wider after all. I am unashamedly a wide-angle enthusiast and the look suits my style (I could argue that the 23 drives my style as I use it for up to 90% of my work). This is not everyone's cup of tea. If I was making the decision now, the Alpa FPS with a Canon 17mm would be in the mix for sure. Do keep in mind that at this end of the focal-length range, just a few mm's make quite a big difference to FOV.
Both the 23 and 28 are outstandingly sharp. It takes more than pixel peeping to tell them apart. I even use mine wide open from time to time! Residual distortion is similar as well. It is there, but it's mainly when I have straight lines near edge of frame that I notice it, and even then, mainly when I'm looking for it.
There are significant differences in size and weight that bear some checking out. As I recall, the 23 is quite a bit heavier than the 28 (but waaaaay less than the 32!). I've read that many use the 28 without a CF and find it acceptable. At the time I tested it, there was no CF available (for the 28) and my view was it needed one. The 23 certainly does much better with the CF and I would never take mine off unless I was desperate for light. It is a large and expensive filter that creates some issues with mounting grads if you use them. I mostly use Blu-Tac to hold my Lee and HiTec 6x4's in place as its quick and expedient in the circumstances I often shoot in. Ugly but effective is how I would describe it. As my camera is a work tool and not an object of vanity, I care only what the pictures look like.
The 23 has one bugbear that I choose to endure for all the other benefits the lens gives me. It is very, very prone to flare when there is a bright source of light near the edge of the image and also outside it. It manifests as a red area the shape of the diaphragm smack in the middle of the image. (Actually, there are 2, one inside another). One can mitigate this with careful shading of the lens, but there are many, many images where the best masking will not eliminate it. One gets pretty good at fixing it in post eventually, but this is time consuming and a PITA. I live with it because no other lens currently gives me the look this one does.
If you are shooting with an Alpa, the 23 cannot be used with the tilt-adapter and if I remember correctly, nor can the 28. I use tilt occasionally with my 40 but can't see any circumstances in which I would need it with my 23.
This is just a quick response with what is top of mind. I'll keep an eye on the thread and add anything further that comes to mind.
Cheers,