I went with Stillen for a number of reasons:
1. Cheaper
2. Immediate shipping
3. Better ground clearance
4. "Safe" noise level (no drone or rasp...no risk of regretting it's too loud)
5. Enhances the car's stock sound without making the car sound completely riced
Some potential drawbacks:
1. Fit and finish is very good but not up to FI's from the pics I've seen (not sure this is a big deal considering it's under the car and the tips look great)
2. Loudness level may leave you wanting more, eg HFCs or testpipes. It's a great improvement over stock and about as loud as I could tolerate...but I still wonder what HFCs would sound like in person with it
3. Less exclusive. Stillen sells hundreds of these. FI's list is available online and has less than 60 installed. If you want exclusivity, Stillen isn't it.
I'm thrilled with my choice of Stillen. The sound and loudness are perfect and leave me the option to do other bolt-ons like HFCs with more wiggle room before I get into drone, rasp, or ear-bleeding noise levels. Many with the FI CBE have taken the HFCs off since it's too loud and drones.