I'd use both, I gather the amp has it's own DI XLR output? so use that and if you want mic up the cab. You may want to play around a little with mic placement to find the tone you're after. Also try listening to each speaker, to find the best one (they can vary in tone).
If you find that the room is interfering with your sound make a little tent around the cab with some chairs and towels to eliminate sound bouncing off of the walls.
I totally recommend both DI and Mic, this method gives you more to work with when mixing.
Best of luck with your recording pursuits.
