Manual every time, aside from the performance difference (which is significant -- you can get a manual 3.0 from 0 to 60 in 7 secs in the right conditions) it's just so much more involving, which makes it much more fun and much quicker on B roads.
If I'm going to be wading through traffic I take the bike, gets there in about a tenth of the time.
as opposed to 7.7 in auto, and still think I can do better 
Oh I
know I can do better, it's just a case of finding enough traction to do it with

. An LSD would be nice and would show up the benefits of a manual even more, but that's a luxury few of us get.
The gearing on the manual is much better suited to low-speed acceleration, as is the fact that you can rev the engine to 4,000 RPM before launching. It's still geared too high for a car this heavy with a peaky 24V engine, but then these weren't designed as drag racers.
Quicker straight-line acceleration is one thing, but it's on the B-roads when you can select the right gear before entering a corner that it really shines. And if you're right on the limit of adhesion with the rear wheels, having a direct link between the throttle and rear wheels (i.e. no slippage due to torque convertor) makes it much safer and easier to control.