My wife has both and I have the "honor" to carry them when she plays out. Katana will be lighter (the DLS40c is HEAVY), more versatile, more reliable, cheaper, easier to replace but there is something in the tone that annoys me greatly, it might be the speaker (I have the 100 combo version), I keep wondering if it was a mistake to grab that instead of the head, one of these days I have to try to plug the combo into some V30 and see what's what.
The Katana will also be better at home for practice, sounds very similar at 0.5W and low volume, the DSL will only give out the goods once it's too loud for an apartment.
I'm still convinced the DSL40c will produce a better tone in a loud band environment but nobody will notice but guitarists so the Katana is the clear winner from every other possible point of view (and a lot of people might even prefer it tonewise).