Magnet Man's stage is much harder than Snake Man's is the difference (Disappearing Blocks > Oh no cloud platforms!) How you can call Snake Man's stage genuinely hard is odd; no death traps til the very end, and they're some of the easiest to get around. This isn't freaking Ice Man's stage where it goes from "Benign" to "OH DEAR GOD THE HORROR!"
Furthermore? Snake Man's pattern is obvious; he only jumps in the middle or on the edge. As such, the strategy is pretty obvious:
Stand on the edge, when he runs to the dip, jump over him, run to the middle, wait for him to come, jump over, shoot as he runs to the other side, repeat.
Needle Man is a MUCH harder fight, and not an easier level. Yes, you get Rush Jet out of it, but that's about it; you don't need Rush Jet much in the initial 8 stages. Needle Man is not one of the easier fights to Buster, as such, not anything remotely close to a good starting choice as a result, unless you really got bustering him down flat.