Striker is okay, if a bit detailed. Ground Zero Games Stargrunt is (IMO) better for platoon-on-platoon up to small company level conflicts. And Dirtside (from GZG) runs from Company to Battalion (though I've heard of larger...).
The former is usually played with 15-28mm figures, the latter with 1/300th, 1/285th, microarmour, 6mm, whatever you call it on a given day.
20mm is a historical WW2 scale and there are a *lot* of very nicely sculpted figures and some *excellent* and *accurate* vehicles done in 20mm. They just cost cost cost!
To me, if you're playing a skirmish game (manouver unit is the individual piece), you want 25-28mm for detail and appearance. If you're playing a squad level game (squad is the manouver unit, or fireteam and you aren't likely to see more than 2-4 platoons on the board period), then you want 15-25mm. If you want to fight combat team or company level fights up to battalion, you need to opt for 6mm.
10mm, though an interesting scale, is Just Another Darn Scale, IMO. I play 25mm (true, as opposed to 30mm+) for squad and skirmish games - I have probably 1000+ figures and over 60 vehicles. If I want bigger fights, I play 1/300th. I have a bunch of microarmour, a pile of GZG sci-fi 1/300th stuff for DS, and a bunch of old Renegade Legion Grav tanks (plastic, about 8 boxes of 50).
What do I like to see?
25mm - because then I can use them in my Trav RPG!
1/300th - because you can fight big fights with them.
Right now, GZG UNSC Marines are about the closest in 25/15/6 mm scales to Imperial Marines. Dark Star/Ainsty/Denizen (I forget who it is...) have some excellent Ventaurians - 25mm in one place, someone else did what appear to be 6mm versions. Get the helmeted ones. And the MidTech marines could easily be any mid-tech Traveller force and do well as USCMC from Aliens fame. GZG has a lot of good hardshell and normal future troopers - NSL, ESU, Mercenaries. A lot of their troops look like they have a 2300 AD inspiration - their alien Kra'Vak have a similarity to Predators/Kafers.
