First, will you be leaving any loads on? like an anchor light?
I thi k that its probably big enough that you do need a controller.
Also, As I'm reading on upgrading my setup, MPPT is not worth
it, because there is not enough to gain, not enough daily drain
on the batteries. Like Charlie, I've heard good things on morningstar.
Also, with the 20, you can increase the system with no issues later.
the 10 amp also would be fine I'm sure.
Rick