Leica's naming conventions actually tell you quite a lot once you know them, just like Canon's. Let's take a SUMMICRON-M 50mm f/2.0 for example. "Summ-" lets us know it's a double Gauss (aka Planar) design, "-cron" lets us know it's a mid-speed lens, and "-M" tells us it's got a fingertip focusing tab and the focal length engraved near the mount.
Without autofocus or IS or different image circles to cover, the deciding factor in choosing a Leica lens, and the only factor that the name could ever tell you, is what max aperture it has. You choose either slow (Summarit, Elmarit), fast (Summicron), fastest (Summilux), or insane (Noctilux). They're all the best lens Leica makes at that aperture, and they all work with every M body.
If we want to compare that back to Leica, all Leica lenses are the better one. It's just a choice of how wide an aperture you need.