The problem for me in the 340 was the leg room, I just couldn't move the seat far enough back (36 inseam). The 421 was better but even a C90 was a little tight for me due to the low yoke.
Joeaksa is right about the GTSIOs. Our 421 was very reliable but only because only two or three people flew it after the factory remans. I'd always cringe when I'd hear a 421 go by with the gearboxes clacking away at low idle
