5 speed or 6 speed?

[Alex-svx]

Just woundring what is the best swap for the svx. I have a old 1990 legacy tranny but want a tranny that is stronger than this one.
So is the best to go for the 5 speed Sti or is the best to go for 6speed?
Lsd or dccd tranny?

(i the legacy has 3.900 and i have a feeling that is just a lot of fuel when i drive it on the highway)

My car is stock and i think it also going to bee that in the future also.

Thanks for help.