For people that doesn't have any rotation of the foot during the pedal stroke, a pedal without float is probably better since you get a more stable pedal stroke.
But if you're even a little bit unsure about this I think getting a pedal with some float is a much better option, I think that having too much float is rarely a injury prone condition, at least not as much as having minimal float since then you're forcing the knee joint to a position that might be completely wrong for you.
Remember we are giving recommendations to a beginner here.
