You have 2 choices with British paras.
Brits, lot of infantry, very large engineer platoon, very light artillery support in the form of the M1A1. No armour, no heavy artillery, Recce options are included as are mortars. Pretty close to pure infantry. get access to a lot of 6 pounders (awesome) and 17 pounders (can kill most things, but have no HE) so always a risk.
Polish Paras.
Access to the lot, 25pounders, Sextons, 5.5" guns, Sherman tank support. Have most of the same things the Brit paras have. Very diverse and effective.
Americans (these vary from Nuts to Market Garden)
Market Garden, lot of infantry, backed up by British Armour and Artillery (heavy arty) won't use many USA special rules.
Nuts, my preference. Access to most of what makes America tick, Tank destroyers (Hellcats) light machine guns, mortars, medium, light and heavy artillery, tank platoons (very late war stuff) armoured platoons (half tracks) and an AOP.
Build the Nuts force and you can field the
MG force easily, by swapping USA armour for anything from your Brit collection.
Other way around is not so easy.
Hope that covers the main differences, I need 6 and 17 pounders to make my brits viable, but have sizeable USA (easy company) and Polish para companies, I like them a lot.
I must admit I find the
MG USA force a tad boring, the Nuts one is very varied. I also built my USA Paras from Glider rifle platoons (I know, shock horror) but it means I can run them as either by simply adding, or removing some teams, and swapping LMG's for
HMG's, Variety as they say, is the spice of life