| I've got a TB-600 and it sounds great. It's not hi-fi, but it does have a pretty good pallette of tones and a really good overdrive channel. Bigger and heavier than a Walkabout, but thirty-two pounds isn't a backbreaker for me.
I've never heard a Walkabout in anything other than a Scout combo, which unfortunately had a bad driver in a local GC. It's a very nice amp, too, lots of fans here on tb. To me, a cleaner sound than the Fender, smaller and lighter, probably easier to try out/purchase in a brick and mortar store.
They both bring the tubey goodness in a hybrid package. If portability is paramount, the Mesa wins. If you like overdrive and need more wattage, go with the Fender.
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"I don't know karate, but I know ka-razor" - James Brown, The Payback | 
