I'd go with Mrs. Voorhees. Neither are very strong physically, but the only confirmed on-screen kill we have from Debbie Salt is when she took Randy by surprise from behind. We know Mrs. Voorhees killed everybody in Friday the 13th and did what she did with the bodies, which took more strength than Loomis showed.
Voorhees is also presumably more skilled with weapons and the environment, while Loomis is your basic suburban mom.