OK, the latest set of Sci-Fi skirmish rules I've been taken with is "Infinity". Check out the web site for more details; the rules themselves are actually free to download although the hardcover retail set has a HEAP of fantastic mini eye candy. If you do like the rules you will probably end up buying the retail copy.
These rules are almost a set of RPG rules rather than miniatures skirmish rules, but the mechanics are really VERY good, allowing both players to competely interact irrespective of who's turn it is!
Anyway, enough of the rules, what I wanted to do here was show a comparison of mins from a few manufacturers including the excellent sculpts from Infinity. I've included GZG, a GW Catachan IG and some TAG SWAT with M4s and a Eureka Modern German with G36; LURV the G36!
As you can see, apart from the Yu-Jing Keisotsu mini in the first pic, the GZG minis are waaaay too small.
The TAG minis mix well but are waaay taller then the GZGs...
The Eureka and GW minis in the last pic look a reasonable match to the undercoated Infinity Ariadna.
GZG do have a good variety of minis including the New Israeli light power armoured and UNSC Heavy Power armoured minis as well as the "Power Armour" figures that will allow you to field pretty much any proxied figure apart from the Infinity TAGs; the old Heavy Gears are excellent for that!
Check Infinity out at www.nomadarachne.com