Having both a 6MT and 5MT, I prefer the 6MT for street driving.
But that may be entirely due to the crappy spacing/syncros of the WRX vs a quality Getrag 6MT.
I'm a firm believer in not hammering a car before the oil reaches its normal operating temp (this may be why I put 180,000 miles on a G60 Corrado and never had to replace the supercharger). The closer ratios of the 6 allow me to accelerate faster when the engine is cold without winding it out or going deep into the boost.
This wouldn't matter at all if I lived in the boonies, but in SoCal morning commuter traffic, you end up merging into traffic or on a freeway onramp before the engine's warmed up.