Some props have 1/4"-3/8" vent holes in the hub near the pressure side leading of each blade. The purpose is to allow exhaust gas to blow out onto the blades to cause some ventilation and a lot of slippage when you first hit the throttle, to allow the engine to immediately rev up to it's torque peak. Same idea as the automatics with high stall speed torque converters back in the muscle car days. This would be particularly useful on props with very high pitch on high speed boats that have a poor hole shot.
How wide and deep are the slots on your little motor's prop? I doubt that they are large enough to cause ventilation, so my guess is that both props will have similar performance. Don't know why they would do extra work to machine slots into forward edge of hub.
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