Bolero is a very tricky piece to get right. There's an unsubtle difference between smooth precision and clunky, deliberate transitions. Especially in this piece, that makes all the difference between the music coming to life, or simply plodding along (as so many critics of the piece contend) to its inevitable conclusion. I haven't heard the Sinopoli version, so I can't comment, but...
I have heard the Boulez version mentioned by TristanLudlow, and I have to say that I don't care for it. It's an excellent example of the complaint that Bolero is repetitive and mechanical. In the end of the piece, where the music becomes increasingly frenetic, Boulez's version feels like it's being played by robots. There is just no soul or presence to it.
The Stanislaw Skrowaczewski recording (conducting the Minnesota Orchestra) that was remastered by MFSL is likewise clunky.
Herbert Von Karajan conducting the Berlin Philharmonic (on Deutsche Grammophon 477 7161) is great. It's his first recorded Bolero (1966), and it just soars.
Leonard Bernstein conducting the Orchestre National de France is also an excellent choice (on CBS). It's faster than the von Karajan (by almost two minutes), and the difference has a noticeable impact the tension of the piece. The overall effect is different, but it's still nicely done.
I really love what Neville Marriner did with the piece on this album--
Bolero; Sorcerer's Apprentice - | AllMusic (
http://www.allmusic.com/album/bolero-sorcerers-apprentice-w5948)
-- and if my CD hadn't gone missing, I'd rip and post it.