I tdhink people need to learn more about MPPT chargers before they recomend against them..... yes they benifit more during bulk charging, no they do not switch to PWM mode, they are a three stage MPPT charger so basicly a DC_DC charger that converts DC to AC then back to DC at the most efficent combination ov voltage vs current. in the summer on a nice day they may only give you an aditional 10% but in the winter when it is cold that number can go up to 40% or when its raining or overcast it will be inbetween. also you could basicly run pannels in series lowering the current while raising the voltage which allows you to get away with a small cable and less loss than running in parallel. if you can aford it it is always worth getting a MPPT controler, if you cant then dont worry about it, but you can always upgrade later, would just mean reconfiguring your pannels to take advantage of a series setup.
Steve