I have to agree with pmark, it is pretty much up to your prefence. I haven't tried homesite in a while, but I remember it being a pretty good cheap alternative.
Just to note, I have always used InterDev and I really like it. This is probably becuase the company I used to work for used InterDev as their standard and I am just used to it. I must warn you though, if you do get InterDev, do NOT ever use it's build it ASP controls (for databinding and stuff). THey are the tool of the devil (or Bill Gates in this case). Just do the code by hand, it is much cleaner and you will learn more.
I recently got my hands on Macromedia's forte into this are, Deamweaver UltraDev, but I have yet to try it out (I will sometime this week, though). I remember Dreamweaver being nice when it came out, so I assume this will be pretty good too.
The only important thing (in my mind) too look for in these programs is support for intrinsic ASP objects. That way you can use typing shortcuts and you code won't get screwed up like Frontpage 98 and older programs would do.
I think both homesite and dreamweaver ultradev shoud have demos avaliable, so I suggest you download those and if you don't like them you can consider InterDev (or even FP 2000, which is newer then InterDev 6.0)
Good luck