Motoring home in a calm does not require much power, thus a small prop would work (and would reduce your prop-generated drag while you are sailing). A geared, large prop will decrease your battery draw, making the motor's battery last longer...but presumably you are not motoring for a long time, so battery life is not limiting. I'd say skip the complexity for this situation: go for a small prop and preserve your sailing performance.
Sailing home against a wind strong enough to get you into trouble, on the other hand, will require LOTS of power. The drag of the mast, sails, and rigging goes up as the square of the windspeed. A large enough prop/motor/gear combo to accomplish this will definitely degrade the sailing performance of your boat. Better, I think, to handle this scenario with seamanship - keep out of trouble by employing your brain before and during your cruise. The main seamanship tip I'd offer is to reef your sails before setting out - match your sails to the wind. The only way a sloop will get into trouble in high wind is if the sail area is too great, leading to knockdowns. Unfortunately, if the wind is this strong, even a propeller may not save you (the boat pounds, prop and rudder are periodically exposed, progress is very slow....been there done that
. About the best you can do is use the motor to assist your zig-zag course home (ie beating with tacking or wears); progress directly to windward, against the waves, is going to be iffy.
If you are constrained to sail in an area where self-rescue is mandatory (along the seashore, for instance), perhaps you should devise another method of rescuing your boat, eg. rowboat or kayak.