I prefer 4th edition, though there's certainly a lot to be loved about 2.2 - it's crunchy and deep.
Regarding 4th edition, the main issues I might look to rework if I was trying to find a balance with 2nd would be to see about revising the attribute/skill system a bit. IMO 12 skills across 4 attributes is simply to shallow for an open-ended RPG - as a result you end up with a couple of skills being required for PCs in order to have a successful campaign. Specifically, I'd love to see Recon and Tech both broken apart significantly into more constituent skills.
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