Have ridden several Burleys and 'tanas, from early models (70s for 'tanas and 80s for Burleys as well as more current models of each brand). Depending on the model/year/components you may notice some differences.
Serotta Legend Ti, Santa Cruz Heckler, Santana Visa TAndem
Back in October, I sold a very early Burley Duet (suntour), that I had since new, and bought a '93 Santana Visa. The difference in the frame is monumental! The butted tubes do make a difference. The bike is about 5 lbs lighter and much stiffer laterally. I was happy to get rid of the 27" wheels, and with a coldset of an additional 5mm in the rear spacing (up to 145mm), I was able to go with a nice modern Shimano 9 speed hub. In my case, the best part is that it fits my wife and I perfectly.