I'm not sure what your looking for limited... Although BBD didn't get into the details, he is pretty much right on.
With any of these programmers, your going to get a couple of functions:
1: More horsepower (up to about 65 max)
2: Possible speed limiter removal (for sure on the Smarty)
3: Possible tire size modification (for sure on the Smarty)
4: Better fuel economy? (The Smarty has a specific setting for this)
They do similar things. Its the HOW they do it. I drive a 6-speed, and I'm 100% satisfied with the Smarty and every function it offers. Others (mostly with automatics) have had surging problems.
In my humble opinion, the Smarty is the hardest fueling option available. I don't have dyno sheets to prove it, so take that with a grain of salt. The Smarty also offers 9 different settings for you to custom tune your vehicle to your wants/needs. It is also the best (once again, opinion) for future modifications. You can choose timing or no timing depending on which wire-tap box interests you (for example, I run Smarty #9 with my Blue Chip FMS: I let Smarty do all the timing. If I had an Edge Comp I would run Smarty #8: Similar program without the timing so as not to cause havoc with the Edge/Smarty timing combining.)
Once again... They all do similar things. The Smarty just does more of them, and arguably it does many of them better.