I ride $50 eggbeaters (with a nice stiff carbon road shoe) and there are no hotspots nor discomfort. As an added bonus, you can walk on the road cleat all you want with no fear of wearing it down.
Power transfer is not going to be related to the size of the platform unless your shoe is insufficiently stiff.
The platform size on a speedplay pedal is pretty much exactly the same as it is for an eggbeater. Cleat size on the shoe is about the same, too.
The crank bros cleats are lighter and much cheaper to replace. They also don't get clogged up by sand and mud.
In short, spend money on nice shoes and just about any pedal will be great.