Personally, as a non-professional I have a really hard time spending more than the mythical 1000€ on a lens. My prime bag currently looks like this:
20mm f/3.5 Voigtländer Color Skopar pancake ("ZE" type electronic mount)
35mm f/1.4 Zeiss Distagon (C/Y mount & Bob Shell adapter)
50mm f/1.4 Zeiss Planar ZE
50mm f/1.8 II
85mm f/1.8 USM
135mm f/2L USM
If I can find a clean 85L mkI for around a grand this year, I'll snap it up if the 'ol bank account can handle it.
For me at least, I want AF on anything longer than 50mm as even with the Katz Eye focusing screen & a magnifier, getting the MF right on the Zeiss 50 faster than about f/2.8 is pretty challenging in situations that involve a moving subject (e.g. candid shots). At least with the electronic coupling you don't have to stop-down manually, which speeds things up a lot.
To address the original post, I'd say that IMHO it's not really an either/or situation. BTW, he didn't really mention what he's planning on shooting with these things (or if he's shooting on FF or crop) so I'll generalize a bit...
There are A LOT of options available in the 50mm department. I've discussed several of them in this thread
so I won't crosspost, but there are certainly plenty of lenses to consider besides the L and 1.4 USM (both of which are good but have their own individual quirks
). The folks in that thread seem to concur that the new Sigma 50mm f/1.4 is really nice but really needs to be used on a body with AF calibration to work well.
Also bear in mind that while the "nifty fifty" f/1.8 II may be physically crappy (build, motor, etc), the optics are quite good and it's the smallest/lightest/cheapest lens that Canon makes. Just get one & keep it in your pocket & you'll never be without a fast prime. (Same goes for flashes & the 270EX II; there's really no comparison vs. a built-in, and if you've got a flashless body then it's a must-have).
Personally, I'm still on the quest for the ultimate 50mm...