Both brands make good amplifiers. I wouldn't bother too much about those extra years of waranty. If the thing doesn't break in the first three years, chances are it will continu to work well. BTW: what are the terms of those extra three years of waranty? Wear and tear will probably be excluded...

The weight would bother me. When you have to travel a lot with the amp, you'll want a lighter amp. Most likely you'll want a flightcase for the amp. That throws in a few pounds also