I'd like to add that their are so many combos out their because they're extremely popular. I have the Mustang LT25 and love it. Very easy to use interface and very popular so a lot of support exists. It also is it's own midi interface so you can record into whatever DAW you're using. It also has a desktop interface which I'm more comfortable with. The Boss Katana is great too just based on it's popularity but I don't know anything specific about it. 

I would recommend looking at the popular combos just because of the resources available. Marshall will always be there when you want to move up but you'll learn a lot more about what you're looking for later by starting with a combo now.