How much difference does the kind of rifle make?

[hoplitis]

Gamewise I'd go for the extra "kill" factor, in a Nam-era campaign. In jungle terrain "fields of fire" can be limited (dense trees) BUT you always need some long range assets to "overwatch" the odd rice paddie, jungle clearing or opposite river bank. So don't forget your machine-gun teams and above all your snipers (veeery useful in Nam games IMO).

I think that the real question is "triangular" M16<-> AK47<->M14 rather then M16<->M14.

Now for a real life comparison ... well I'll leave that to the experts.