I currently use a Peavey TNT 115 and an Ashdown Touring 220, also with a 15" speaker. They are both really great amps in totally different ways and they really don't sound anything alike. The Peavey is just as you would expect. Solid, powerful, a lot of features and a basic clean sound that is great for a lot of kinds of music and perfect to run pedals on to sculpt your sound. The Ashdown is punchy, bright, and with it's tube preamp it has a very satisfying growl. It has a nice EQ, several sound changing switches, and is smaller and lighter than the Peavey by quite a bit.
Honestly I love them both, even moreso when used together (with a Peavey Basic 112 on top running my highs). If forced to only keep one I would keep the Peavey because it is more versatile in my opinion, but I'm happy I can keep them both. If I didn't want to use pedals or anything but a bass and a cord I would probably choose the Ashdown because it really does sound good and the tube preamp gets that tube growl going on real nice.
I know these are not the exact amps you are thinking about but they are similar so I thought I would share my thoughts. I think the Peavey is probably the tougher of the two, I can see it outlasting the Ashdown... Hell it will probably outlast me!
Bass - Vocals - Songwriter of Energy Slave
Fuzzrocious club #188