So let me get this straight, you're used to driving FWD and want to make a 400+ hp RWD sports sedan your new daily driver? I hope you have money set aside for new winter tires, or an excellent insurance policy.
That aisde, if you're buying something as a daily driver, and you're a recent grad, even if you land a job that pays 60 grand a year (which is even generous for someone our age) you'll find it difficult to afford the big car payments, gas, insurance for your M3 or M5 (just wait till you see your brokers face) with your other bills. That being said, you might be rich, and just looking for a fancy car to fly around in, and if thats the case go with the M5. IF you want to save a bit on gas and insurance, go with the M3. Keep in mind the E90 series of M3s were the only ones to have a V8, so this may make the car somewhat of a collectors item in the future, or at least help it to hold it's value better.
As for all season friendly, you might be better off looking into an Audi S4 or A4 S-Line, Quattro (AWD) on either. If you can afford it, even go with the S6 Quattro. BMW 335i and 550i with xDrive are also nice alternatives. I'm guessing you're not into Benz's, but if you are, dare I suggest the c350 4Matic?
Happy hunting!