Depends on the handle style.
At this point, the Mag Handles have just felt better for me on the Fusion series. My hands are not HUGE, Large to XL in glove size, but the standard grips tend to feel too flat on the Fusion series. The Mag's contours seems to provide me with a firmer Grip. Pretty much the same experience with the TAC series.
On the Ergo blades, given that unless it's a custom shop piece didn't really have Mag handles, they feel amazingly comfy. Better than the Fusion series depending on the use. With the EDC blades (Meaner, AD, GW), I like the standard handles over the custom shop fatter handles as well. The smaller handles seem to give me more confidence when using them for slicing or other small utility work. I'll gladly reach for my OJ GW or my thinned out Ban modified Meaner, than my Fat Hog's Blood Warden or my custom shop AD (fat handle).
Sum it up:
Mags on Fusion and TAC series
Standard on Ergo series and EDCs