I haven't had any problems with my Edge (knocking on wood) but it really depends on what add ons you are going to do. If you are staying mostly bolt on w/o any major internal work, an Edge would be fine. However, when you start doing heads, cam, turbo, etc. the Edge won't reflash the truck, it will only add the extra HP and TQ based on a stock/bolt-on pre made up sort of deal. The SCT actually reflashes your truck based on the mods YOU HAVE INSTALLED. Much more customizable to whatever you can throw at it.
I didn't know this when I bought the Edge, and I plan on doing some engine mods, so I'm going to sell the system and replace it with the Edge Insight for parameter readings, and reflash it with the SCT. For optimum performance and best all around for you and your truck, an Edge Insight with the SCT X3 would probably be the best thing.