I love Rapid- every component I used except for heat sink, controller and wire, was from them.  They are very reliable, very helpful and they sell quality LEDs.  

The dimmer on the Rapid kit is actually pretty decent and has some nice functions- read about it and decide if its EVERYTHING you want and compare it to the AI functionality...  This may make the decision easy.

IF you think the dimmer controller is adequate on the Rapid kit, or better... then

consider if you want it to look like a commercial fixture, if so your looking at serious shop time and very careful work.  I mean hours that run well into the 40-80+ hour build time- its not a trivial project to make it really look good and have high end function.

Also- consider that it is relatively easy (if you make a mistake that should not occur if you test your circuit before powering on) to fry all the LED's in a string... and Rapid will NOT replace LED's you fry by being careless.

A warranty is worth something, but in reality, if you power up a DIY fixture, and don't blow it up and don't pull off a wire or have a really sloppy solder joint fail, these don't really fail very often.  The only part really that would fail in any reasonable frequency would be the dimmer, and Rapid may warrant that and its pretty cheap any how.  LEDs once they have been shown to power up and run, don't have a super high fail rate- at least not the quality LEDs being used in these kits and the AI fixtures.  So I would actually say the warranty is nice but in the case of the DIY- not a big deal, and with the AI-nice to have since you didn't build it and cannot repair it.  A single LED failure in a DIY rig is like 3-7 dollars to fix.