I have a hard time using anything other than a small GBB as a sidearm, as in a 1911 or block of some sort. I tried running other things that gave me more firepower but it is just a pain in the ass. Having been running a l96 at the time, it was already big and bulky. Adding anything to my kit besides a standard GBB sidearm proved more harm than good for me personally.
Despite using the ghillie and "staying low", it is airsoft, and I find myself having to make quick fast movements across open areas to even get to the woodbine at the field I go to. With that said, I would be far less mobile with anything besides my 1911, and would be worrying about something bigger getting in the way/breaking on me.
Plus, I'm not going into a house to clear buildings unless I really have to. Being the guy with a sniper rifle, I try to stick to my primary weapon whenever possible. As in providing the cover from the perimeter while others go in and do the dirty work.
My 2 cents.