Big or bigger?

I'm about to buy my first ride, and have decided it doesn't matter that much if I go Suzuki or Kawasaki (feel free to correct me), especially on the -1000cc bikes (I don't really know about the 1500cc's yet since I didn't do any research on those yet)

I started looking at prices, and what do I see: only €1000 ($1550 today) difference between a 2006 Vulcan 900 (kawa)15000km all-in except Mustang seat, sissybar-luggage rack and windshield
and a
2003 1500 LT (suz)30000km, €7300, all-in except Mustang seat.
Both mint condition, btw

I'm planning on touring (read: two week trips (doing 4000km) are no exception) so maybe even bigger is maybe better, considering I'll take my girlfriend on some long tours as a passenger.
I'm confident the 900 or C50T would do the job, the question is: will a 1500 do better?