OK, Sam.
The infantry, tanks, Artillery, IFVs and recon vehicles are all from Oddzial Osmy's (O8) 3mm moderns line. The IFVs, for example, are simply West German Marders given a sci-fi paintjob and the Infantry is modern Soviet kit.
My rationale for this is that armored vehicle technology is now mature and while a few things change – mostly in weapons and countermeasures – by and large today's AFV look is still standard throughout the Human Sphere. The Sphere has not gone over 100% to mecha because these are based on imported alien tech and are hellishly expensive.
The real world rationale is this: I prefer the detail on O8's stuff over anything I've seen yet that's specifically been made for 2 or 3mm Sci-Fi so I'll continue to use their figs.
The one exception to the rule is Germy's 2mm infantry, which I use as armored infantry. It's sold via Ground Zero Games and you can see a few of these figures on the base of the Lafitte Regiment's titan.
The Laffite's line mecha are all GZG not-Votoms, as mentioned above. The support mecha, Stalkers and Sloth HQ units come from Iron Wind Metal's "battle armor" made for Battletech. Many of these figs are easily repurposed as 3mm mecha and they cost about USD 0.50 apiece:
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The 3rd's titans, both light and heavy, are repurposed 1/144 Dream Pod 9 figures from their Utopia & Eden line.
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The DP9 stuff are far and away the most expensive components of my 3mm sci-fi armies, the large titans clocking in at around 11.00 USD each. Even the GW stuff is cheaper: I got 3 Tau battlesuits for about 8-9 bucks apiece. It's undenaibly beautiful kit, however.
By contrast, the O8 figs which make up most of my armies cost 4.00 USD for 15 stands of infantry or AFVs. So while you're looking at maybe 80 dollars worth of figures on that module, when the armies expand out to their full size, the cost is under 200 USD for bopth together.
You can see the 3rd, fully deployed, below: