996 c4 cab. 3.4 or 3.6? What to look for

[A.N.]

Evening all.
Been thinking of getting into 911 ownership and I'm set on a 996 c4 cab to have alongside my 944 s2 cab.
What do I need to look for in buying, and which is the better platform, 3.4 or 3.6? It won't be a daily, but good weather fun.

Thanks in advance for the advice and replies