why do you need the 1.4? not even considering the 1.8? 1.8 is already pretty good not to mention very sharp. probably the best bang for the bucks lens there is out there at $100 off clist.
im a nikon guy so i wouldnt really know about the canon 1.4's. however ilvtofu has the sigma 1.4 and says its surprisingly better than the canon version. (has more blur because the lens is bigger)
are you shooting people outdoors? if you shoot wide open at like 1.4 it will overexpose like crazy. im just guessing you will shoot wide open since you want the 1.4.
as for myself i at one point had a 1.4g which is 4 times more expensive than the nikon 1.8. loved it. build quality is much better and the lens had a really nice feel. sort of like a canon L lens i guess.... i had a super sharp one and bokeh was creamier than the 1.8. loved that lens. but i ended up selling it for a tamron 17-50 fixed f/2.8. was it worth 4x more? if i was made out of money i would say yes. sadly im just a teen and a 50mm wasnt really convenient to walk around with
give the 1.8 a shot? i mean its only a bill whereas the 1.4 will be 4x more.
sold and upgraded a lot if not all of my lenses but i still have my 1.8 nifty fifty