Physically, the 9 and 12 are the same size, just different power plant/delivery. Not ridden a 9 though so can't give any feedback on comparison.
Support wise, nothing now from Harley Davidson and also a big issues with HD Parts delivery to Europe at the moment. Support comes from specialists: e.g. Maz at the Emporium in Manchester and parts supply (for what they can get) from Riders in Bristol. If you're seriously considering ownership, suggest calling Maz (see here: http://www.ukbeg.com/forum/viewtopic.php?f=7&t=18897
Had my XB12X for 15 years, know it intimately and generally been reliable though last year some electrical issues (now resolved) caused the need for a breakdown truck on more than one occasion.
My personal view is buying a Buell now is akin to buying any old model bike. You have to be prepared for things to go wrong and if using for commuting, to have a back-up plan.
Ownership can be a fantastically rewarding experience with the right bike.
Buell owners should be committed