Just out of curiousity, what do you guys think is a better feature on a WWII low-wing plane. Retractable gears or flaps as a 5th channel?

Also, if a plane has retracts but no flaps, how hard would it be to add flaps to the wing so there are 6 usable channels? Would it be harder to add flaps or retracts to a low wing that lacks them? I need to know for my plane selection.


Thanks!

Kevin