What do you guys think are the differences between these two?

In terms of (1) Long-term career prospects, and (2) Barriers to entry?

I take it that getting into network security requires a help desk job beforehand, while an application security career requires being an active developer first.

P.S. Can someone please tell me what I can realistically expect as a starting salary for a Tier II help desk position? A tier I?

Any tips as to knowing which help desk jobs are better for career advancement? I keep getting stories about people working as a help desk person for more than three to four years without any promotion.