We in our unit always thought it most important not to leave any weapons behind for the enemy to capture!
Of course it always depends on the actual situation the crew is in.
The M60 was a fantastic weapon. Ours in our slicks were of course those with the double hand grips, ie M60D's.
After getting shot down during TET 68 and spending 5 days in a small outpost fighting off the VC we were thankful that we had our two M60D's, two M-14's and our two 45's.
A great advantage of the M14 was that it used the same ammo as the M60!
This was of course not the case with an SKS, AK