There is no arguing preferences.In fact, loosing the 4:3 ratio is one of the major issues thats keeping me from the switch.
Everytime I use my Nikon, I get the feeling that there is not enough room for the picture. As I do my Beauty shootings almost in Landscape format, this is really a big thing for me.
S.
Personally, I've had little issue with the ratios since most of my other cameras are 3:2, and I'm used to composing with that ratio. The S viewfinder is nice and big, so not the same as looking through a 35mm DSLR tunnel.
When I was considering the S system, I got one to compare to my H4D/40 for a week ...and even when slightly cropping the S file and upsizing it to the size/ratio of the H-40, it edged out the H4D/40 ... IMO, mostly due to the Leica optics which are ground up designs for digital and require far less DAC corrections, or none.
In the end, the S2 was added because its handy form factor, and firmware improvements that basically eliminated the need for a full 35mm DSLR system ... all while taking over many of the more mobile/travel duties I used the H4D/40 for. I upgraded the H4D/40 to a H4D/60 which is clearly superior to the H4D/40 and Leica S2 for many more demanding applications ... and the Dalsa sensor is renowned for the rendering of skin tones ... in both natural and artificial light ... to my eye, something I found to be true.
IF you want to spend money on gear, given your subject matter, I'd consider upgrading to the H5D/60 ... which, with the trade program would be less $ than the Leica S body alone. The new 50-II is amazing on the 60, and the DOF with the 100/2.2 is even more delicious ... The 210/4 comes into more play on the 60 than on the crop frame 40 for head-shots and the like. The new HCD-24, the 28 and the 35-90 zoom produce the slight crop in Phocus but still retains 56 meg delivered in a frame still considerable larger than the H-40 or Leica S
Otherwise, I'd stay pat.
-Marc