Like all these comparisons, it depends on the individual horn and what fits best for you as an individual player. In general, both of these are great horns with the TH&C usually given the edge as the top of the vintage Buescher line. You might find it useful to look at Steve Goodson's website (saxgourmet.com), particularly at the vintage horn value guide. For alto, he lists the TH&C as worth about $500 more than the Aristocrat Big B. That again though is a generalization and you need to try out the horns. Value is not as important as how the horn works/sounds for you. I have a TH&C and have tried the Big B. For me, intonation was better on the TH&C, but that's very anecdotal. They're both exceptional horns.
---------------------
John