it's all up to you on what you prefer out of those two. the thing I like about the ARES Scar is that it's modular. Need an indoor cqb rifle? you can swap out the outer barrel and spring for cqb length and fps limit. Want a DMR for outdoor play? swap the outer barrel to the sniper length one and change your spring. barrel swap takes 10 seconds, and spring change takes a minute.
That was my choice though, I didn't want to have multiple guns for different purposes when I could have 1 to suit all my needs.
CQB length outer/inner barrel combo
Sniper length outer/inner barrel combo