broadband is better as in you can use the phone at the same time as being online, evrything loads faster and if you get an unlimited connection package you can be online 24/7 but it does cost more than dialup, cost depending on how fast you want the connection.
If all you use your connection for is surfing the net, checking emails and chat then basic broadband (512kbps) is plenty good enough and you can get it for less than £20 unlimited use.
If you want to use your connection for downloading etc then depending on how much you want to pay a month and whether or not your phone line can handle it, basically the faster the better.
Have a look at
http://www.ukonline.net/broadband/comparisononnet.php these are one of the few isps left that do offer truely unlimited connection.
Steer well clear of homecall and tiscali, particularly if you want to download, they frequently limit your speed and don't like admitting to it :rolleyes:
HTH and feel free to pm me if needs be :)