The crank isn't the weak link, it's the rods and pistons. I went with Diamond Pistons and Manley rods along with my stock crank. The stock Nodular Iron crank is a stout enough piece and unless you're planning on pushing things past 600hp or 6,500RPM, I wouldn't even bother replacing it.
....as for the Nitrous vs Blower thing. Totally different animals. The nitrous will be cheaper, but the blower will be there all the time. S'up to you, I guess.