It depends where you are and what service/speed you plan on subscribing to. I have Bell DSL and have had it since it was available. I have had no problems with either service outages or speed slowdowns or my e-mail service in years. Most of my clients who have DSL have very few problems while those with Videotron have frequent problems with outages and e-mail bugs as Videotron tends to blacklist domains very quickly as spammers due to the spam filtering system they use. If you always use webmail providers like MSN or Yahoo, that won't really matter to you. I also find Bell customer service to be much better, at least for corporate clients. One client called Videotron for info about switching from Bell 4 times last week and never got a call back with the info they needed. Needless to say, they have just upgraded with Bell.
But overall, most people I know are happy with whatever service they have. It's not like a few years ago when outages were frequent and cable had serious slowdown issues. Go with whoever you feel comfortable with.
Oh yeah...one warning about Bell and DSL in general. Find out how far you are from the central distribution outlet in your area. The closer you are the better and if you are more than 4 or 5kms away, go with cable.
Techman