Re: Which way to go?
If you do a fixed 10x you will need an alternative sighting system for any close shots since the target gets out of focus and the field of view narrow when the target gets up close. If you can add a red dot sight for those circumstances it may be OK. I had one of the Bushnel Elite 3200 10x scopes on an AR and I hated it. Then be sure that the turrets and reticle are calibrated in like units.
If targets will only be engaged past 50 yards, then a fixed 10x will be a lot more comfortable. Having said that, there are several very good Vortex scopes in that price range all SFP but with effective reticles and turrets and a good adjustment range and variable magnification. No doubt a variable magnification scope is a lot more versatile than a fixed one.