I actually have seen a tank made by Reef Savvy and honestly I think that it is a very beautiful tank; however, the tank was rimless and did not have a canopy. If you do not plan on having a canopy, then I would love a custom, rimless reef savvy tank over a manufacturer tank, but if a canopy is involved then it is a waste of money, just my opinion.
I disagree with you on the custom tanks. Sometimes people wants a certain size tank, different style over flows, low iron glass, or thicker glass. It is the option available that make having a custom tank great. Commerical made tanks are produce a certain size and style and to some hobbist that is not good enough.
Beside, it would be scary to have a rimless tank in a very large tank.