I can give a little personal experince. I have an 08 GSA. Last summer I blew up the tranny out in the NV desert NW of Gerlach.
A new Enduro tranny was around $3k so I looked for a used one. Looked for months and finally found a standard one w/ only ~9k miles one it for $1250.
I've had it out a few times since treadless & I installed it in December. Starting takes a bit more clutch but once you get going, it doesn't matter. The only this that would be a real clutch slipping occasion would probably starting on a steep incline. The higher 6th gear doesn't seems to improve the mpg much if any, but I haven't had it out for any kind of significant distance. The more relaxed engine RPMs at freeway speeds is nice. Acceleration and passing is adequate w/o downshifting, but you might have to drop a gear on a long grade.
So for me, at least, the standard tranny is going to work out just fine.
Equal to all of you of roads and good luck! - krokodil al-kashi
“We are turning into a nation of whimpering slaves to Fear—fear of war, fear of poverty, fear of random terrorism, fear of getting down-sized or fired because of the plunging economy, fear of getting evicted for bad debts or suddenly getting locked up in a military detention camp on vague charges of being a Terrorist sympathizer.” —”Extreme Behavior in Aspen,” February 3, 2003
"The State sees the spectre looming ahead of terrorism and anarchy, and this increases the risk of its over-reaction and a reduction in our freedom." - Stanley Kubrick