.Net setup vs InstallShield

Question

Currently, we're in need of deciding quickly if we'll be using .net setup or installshield. In my previous company, we used installshield (9 or 10, can't remember) but I did not bother asking why, and what is really the advantage of using installshield instead of the built-in setup project for .net.

Currenly, we only have installshield 3.1. Is it worth sticking to it? upgrading it? or going .net setup? And why? I've just started searching for articles regarding this but haven't found any concrete answers yet.

If you have any idea, suggestions or comments, it will be greatly appreciated. Thanks!