If they don't leak and sound like S***. I had some E-cutouts on my G35 for a while... It was cool for a while-- seems like every mazda speed3 and srt4 teenager has something close to no exhaust and it all sounds the same. Plus mine leaked like crazy and ended up sounding pretty terrible when closed.
Like a dirty turbo diesel.
Save your pennys and get someone who makes custom exhaust to do one for you- It saves money and you get EXACTLY what you want.