Historically, there have been a number of slide printing schemes, such as Cibachrome (well known for having vivid colors), but these have all been largely obsoleted by scanning and digital printing. You avoid all the noxious chemicals, and you get excellent output. (And, as a nice plus, your lab only needs one color printer that doesn't care whether the originals were on slides or negatives or digital or whatever.)
As such, the question you really should be asking is what's the best slide scanner. I've heard many good things about the Nikon scanners with "Digital ICE" (which uses a fourth wavelength of light that tends to highlight dust and scratches, allowing for automatic cleanup). At the higher end, a friend of mine swears by his pricey Imacon. Commercial slide scans are done with drum scanners. You pay big bucks for drum scans, so you only do those for your serious favorites.