what's the difference between 60/40 and 50/50 solder?

I always make my beginning students cut glass with a $2 cutter, and solder with 50-50 for their first experience. When they move to a carbide super cutter, and 60-40 solder, they can really appreciate the difference. 50-50 is lumpier, not as shiny or as easy to get a nice bead with. That said, I know many folks that use it exclusively. Go figure?

I remember reading someplace the the different alloys also have different "open" range. (upper/lower temperature limit where the solder is nicely workable.)

I seem to recall that there was a third 63/37 blend that is supposed to have a really narrow "open" time/range that is used for sculptural solder.

I googled around to try and find the page, but couldn't. sorry.

Does this match people's experience?