To not add to all of the rhetoric about light and fast vs. slow and heavy, but to answer your last question, these are the 2 .38 Special +P loads I carry in my 340 (which can chamber .357 magnum, but I find too punishing):

Speer 135 grain GDHP+P (modern design with a great track record)

158 grain LSWCHP+P (Chicago, St Louis, FBI load-great old design, great record; I carried this as a duty/off duty load while working as a police officer in northern Chicago suburbs 30 years ago, very similar to your weather in Wisconsin. Any manufacturer will work, I prefer Federal Nyclad if you can find them.)