Hmm. What do you mean by ultimately equipped? As in equivalent optics and such to hang off the rifle as to make it equivalent in price to two PS90? (Thats some pretty decent optics to perform a variety of roles
If we keep it in the context of this 'fun' hypothetical situation, and fix the variables to just the parameters listed, then the 5.56 for sure.
I've been toying with the idea of getting a PS90. But I'd have to go with the FS2000 and a backup FiveSeven. The simple reason is 5.56 just has better performance and energy:
5.7x28 (approx 400 ft/lbs)
5.56x45 (approx 1250 ft/lbs)
It can do everything the 5.7 round can and more in terms of ballistic performance. Also, no round restrictions on 5.56.
Yes, same ol' argument about the 7.62 vs 5.56 that goes on to this day. Less ammo or more capability.
But like a previous poster indicated: just get all 5
on a side note... do you guys ever get a blood blister/skin pinched on your palm while locking in PS90 mags? I must have done that 4 times already. Ugh!