I think aweber is the best, maybe getresponse too, all other had way badder delivery rate in the tests that I saw online. Only getresponse is gets more expensive above 1000 subscribers, the more subscribers you have. Aweber has the same price up to 10,000 which is great.
But I don't feel very good with awebwer because I have read the stories of two people where aweber has very relentlessly kicked them after they made a mistake against the TOS. No opportunity for explanation or another chance. They kept the pre paid money for some months. Ok, to keep the prepaid money is also in many companies TOS but that somehow sucks. You don't need to have a bad intention, only a little mistake, and you have a big problem.
With Mike Filsaime they have not being relentless, they only told him, that he was doing something wrong (against TOS) and he corrected that and all ok.
So it looks like they are only relentless to the small fishes...