Heh 2000 try 5000, I agree with you for 99.9% of people the AEM is all you need (and more). There is however great benefit in using an ECU like the motec if you are willing to spend the money to have it installed and setup. There is no limit to what you can do with an M800 or better and some really cool setups can be had for the money so if cost is no concern motec is your ecu. You could very easily spend over 50k setting up and installing a motec if you wanted to...

The AEM is perfectly capable of controlling a 1500hp + motor and when properly setup will respond as well or better than an OEM ecu in most conditions making it the obvious choice for most people.

Personally I'll take the motec though, if you have multiple project cars (or anything else with a motor) you can use the same ecu in all of them. If you can do the install, setup, and tuning yourself the motec is definitely the way to go.