Been buying infantry from a bunch of companies lately so figured I'd share a few thoughts.
I have moderns/cold war fig's so far from Peter Pig (australians for vietnam), QRF (west germans and soviets), Eureka (modern russians), Battle honors (soviets) and Khurasan (more soviets, you may notice a trend here).
(I have some vehicles from old glory and battle honors too)
Size wise, I'd say QRF and Khurasan are fairly close to each other. The QRF ones might be a tiny bit bulkier but the two would look fine together without any real concerns.
Khurasan is definitely the largest of the selection. Setting them up alongside the QRF figures and mixed in together, you can't easily pick out which is which but if you hold them up side by side, they're a tiny bit taller.
Peter Pig is a bit shorter height-wise.
In all the cases, they're good quality as well. You get a few different poses (though make some squad leader types already) and they look very natural.
I'd say the Khurasan stuff is maybe a little more animated in poses and the Peter Pig figures have the unique "running and shouting" PP look.
The QRF ones look the most like they are actually in a fighting position.
The Eureka figures are lovely. Lots of different poses and great detail. Very crisp too.
Only one problem. They're a head shorter.
I put a standing Eureka figure next to a crouching Khurasan one and they're the same height!.
On opposing sides, I imagine no one would notice but they'd be hard to mix in the same unit.
Eureka and Peter Pig seem to match each other nicely.
That's not good or bad as such, some people like their figures taller or shorter but it IS worth noticing if you're in the business of acquiring modern or cold war figures.