I had my eye on the GT1 B for a while as it doubles up as a portable headphone amp, plus the presets are nicer than those on the amp.
It was a moment of madness getting the GT1 B but no regrets, at least it has a built in tuner unlike the katana.
I also have an aversion to using apps, ..... I can't be the only one?
Having said that, the Katana is a great little amp, plenty of volume plus great low level performance and the effects that I do use are nice but some of the presets esp the synth based sounds are awful.