Some time ago I was questioning myself the choice between 50 f/1.4 and 85 f/1.8. Ive chosen 85 f/1.8 mainly because 50 f/1.4 is not so sharp wide open and the AF (micro type USM). I think that 85 f/1.8 is a great lens in terms of IQ/price. Little bit CA wide open, but its managable. Great for portraits, candids, gigs (with enough space), street...
This year I bought 28 f/1.8 USM and I think its a good lens (on my 450D). You need to stop it down a bit (to 2.2) to achieve good contrast. But it is usable at 1.8 if you post process and tweak it a bit. I even like bokeh from this lens. Good lens for indoor shooting.
I also have 40 f/2.8 STM. Its really a bargain. Sharp wide open, very good contrast and colours. Bokeh is also really nice. I have not tried it as a portrait lens yet but Im sure it will perform very good. And when I have it mounted on a gripped body it looks really funny
...so when Im going out Im always choosing which to bring: 28 f/1.8 USM or 85 f/1.8 USM. 40 f/2.8 STM stays always in my bag About 50s
I had a chance to shoot with both 50 f/1.8 and 50 f/1.4. For me, 50 f/1.4 is not that better to justify price premium over 50 f/1.8. I have also tested Sigma 50 f/1.4 and if I had to choose I would buy Sigma - it is sharp wide open (at least the tested copy was).
...and yes, I would prefer to choose Canon 50 f/1.4 if it performs just like Sigma even with a higer price.