I've driven a 3.2 manual but not that extensively. I'd say the difference between auto and manual is
much less than 2.6 vs. 3.2, i.e. a manual 2.6 is still way off the pace of a 3.2 auto.
TBH, I feel that whilst a 4 speed auto will by necessity have a pretty tall 1st gear and be a little slower launching, the manual Omegas have the opposite problem where 1st gear is very short for a reasonably powerful car and the manual box and clutch aren't really suited to the quick changes this necessitates if you're going to launch it quickly. Once underway, not sure there's much in it performance wise, except the manual is more often in the correct gear for the road ahead!
I do sometimes wish my 3.2 was manual due to the shortcomings of the auto gearbox, but at the same time, I wouldn't want to live with the standard manual setup either. If only I could just drop a T5 gearbox in...

Might even be as simple as removing all the sloppy rubber from the standard shift mechanism, I suppose.