Its an age old question that a lot of people get hung up on.
Personally I'm with (and have a bias for) Makita. But if you're set on dewalt or makita, you can't go wrong with either, check the current offers, decide what you really need/want and go for it.
Makita seem to have the largest range from the big players, which is what swung me that way.
They also do the "best" multi tool with their Starlock dtm52z. They're more expensive for the blades due to the fitting (I'm still weighing up this item myself), but the reviews are highly positive.
I'd also consider Bosch and Milwaukee as they both come highly recommended