Basically - whats the difference?
Pendraken-wise, the 1812 Moscow figures were done a long time ago now, and were never fully finished off. They were sculpted by a different designer, but do actually look OK next to the new ranges. Hopefully, the new Napoleonic ranges will slowly expand over the next few years to cover as much as possible.
Historically speaking, there are a few variations in some of the figures, but someone with much more Nap knowledge than me can help out there!
I'm really wondering if it makes a difference which ones I buy for the french,and how multi period they are. I want Russians as the opponents, but want to be able to put the French up against others as well (probably Brits)
I bought an 1812 French Army when they first came out. The infantry are Ok they are in the pre 1812 uniform which is fine but they have the over the knee gaiters which for me limited them somewhat. Did not care much for the march attack pose which seemed very stiff and there is a bit too much height variance in the figs (e.g. the drummer was about 1mm taller than all the rest and the eagle bearer tiny). I would recommend going for the new infantry figures rather than these. The Lancer figures though are absolutely superb and I rate them very highly. The Polish and Wurtemburg infantry are simply French figures with different heads so not really suitable for what they claim to be.