A font can contain arbitrarily many glyphs, each of which has a unique name. A number of such names are standardized, but they are different from the names given in the Unicode character set. The encoding vector can be changed on the fly. Type 1 is capable of producing very high quality fonts, both for high resolution printers and low resolution screens, subject, of course, to the quality of the rasterizer and the hints. The speed of rasterizing is generally very good.
Scalability only refers to linear scaling.
Differences between the two are probably unimportant. Commercial rasterizers are available for most platforms, many are also built-in to printers and plotters. A low quality free rasterizer is available for most platforms in source form inside Ghostscript. Since X11R6 it is compiled into the core X library. Partial downloads are not possible.