List building suggestions

I've never really gotten into email marketing prior to this, but I think I'm going to bite the bullet this year and finally grow this part of my business. I've done fairly decent this year with my online efforts and I need to take some items off the taxes anyway. I've been looking at going with wither aweber or get response for this service. I've heard things good and bad about both

I'm wondering if people who do this can pipe in on which of these I should go with. I have always heard that aweber gets better delivery rates, but at the same time getresponse seems to do okay with this too considering the amount of list mails I get from people who use getresponse.

So I guess it comes down to the extra reporting metrics you get with aweber, but I'm wondering if these additional stats are worth the additional cash it costs. After all Revenue - Expenses = Profit

Since I'm new at this the stats may very well prove very useful and allow me to reduce my learning curve. Thoughts?

The other thing, if you get one of these services do all your users have to stay on a single list? For example, if I had an IM list for one site, then could I also have another list for weight loss from another of my sites and keep these separate? I'm pretty sure the answer to this is yes, but I wanted to make sure as the FAQs i read on those sites where not really clear.