All three are excellent pipes. The Sceptres have the added advantage of being stainless and require no additional mounting hardware (you need to remove and use the stock hangers for the others).
The Bubs and the Tpipes are very similar in that they were both specifically designed for the Triumph to gain max HP and torque. Totally different sounds too.
The Sceptres are by far the loudest. Can't really say about the gains in HP though.
You really should look and listen to them before you buy.
Come over to NY in two weeks, they will all be present.

A word to the wise is not necessary. It is the stupid ones who need the advice. Pat