As I understand it, the difference is not so much between service providers as between [a] dial-up [b] cable [c] DSL, i.e. the type of service. We all know about dial-up, I won't bother with that.
The difference between cable and DSL is that with cable, you share a connection with sometimes as many as 300 other subscribers -- it's like a party line -- whereas with DSL, the connection is yours alone.
If traffic is not heavy, you won't notice any difference -- or not a significant one anyway -- between these two types of service. When it will make a difference is at peak times, when all your neighbours are using the connection too. The total capacity doesn't change, but now it's being shared. If you're on DSL, it doesn't matter how many other subscribers are online at the same time, because they're not on YOUR line.
Bottom line: If you're in an area where the number of subscribers on one cable connection is low, your performance probably won't take a hit. If you don't use your connection at peak times, your performance probably won't take a hit. If either or both of these issues is pertinent to your situation, you're likely better off with DSL, and any DSL is significantly faster than dial-up.
For what it's worth. Good luck.