RE: over kill
I agree 100% - shot placement is key. I also think too may folks get all caught up in high powered magnum rifles. A .243 vs a .300 win mag is a perfect example. Both will kill deer with the proper shotbut hunting styles must also be considered.
If hunting from a treestand, I would recommend either. But, if tracking deer in the snow is the strategy, shooting at a running deer, multiple times,will probably come into play. In that case, I would certainly go with the .243 because it kicks much less than the .300 win mag and my chance to get back on the deer would be better using the .243. I have shot both and in my case, I find it takes a little more time to get back on target using the .300 win mag. A little more very vaulable time.
Just my 2 cents.