Upgrade or Prime time?

Well I have some money burning a hole in my pocket or more to the point £700-00.

I shoot motorsport mainly so my most used lenses are 70-200 MKII for pit lane and 400 prime for track along with a main body of a 1DX and a backup 7D which I use with a 17-40 F4 with a 580 EX for grid shots.

When not on track I have been taking pictures of my two boys and general stuff with a not very often used but very good copy of a 24-70 MKI which to be honest spent most of its time up until recent months stuck in my kit bag.

I had a mad moment and decided to buy a Sigma 50 1.4 as I used to enjoy shooting with a Canon 50 1.4 on my 1D MKIII a few years ago and liked the better build of the Sigma along with some lovely shots I had seen from this lens. After I sent back my third copy for either having back focus problems or being very soft up until f2.8 I now cant make my mind up of which way to go.

I can sell the 24-70 MKI and upgrade to the MKII for better IQ and colour reproduction within my budget but I also like the look of some of the images I have seen from the Sigma 35mm F1.4 but don't know if there are as many copy variations with this lens as the 50 1.4.

My other choice I now have is just to spend a little more and go for the Canon 50L 1.2 as after seeing some posts regarding the colour reproduction from this lens it has me rather tempted to start collecting primes again although it is colour reproduction rather than low light I am interested in which brings me back to how good the colour is from the new zoom LOL.

Any one care to add anything to help that owns any of the above would be most helpful.

Well, I wouldn't buy a 24-70 II if you dont use the one you have now.

Nearly all Sigmas I have ever used have large copy to copy variation.

The Canon 50 1.2 is an amazing lens if you can afford it. I borrowed one from a close friend and it pained me to return it. That being said, the Canon 50 1.4 isn't a bad lens either and is certainly good for the money.

So, in summary, I would go for the prime based on what you said above.

Why not return to (y)our roots and get yourself anothe Canon 50/1.4??

I get on fine with the Canon 50/1.4 & IMO mine is of reasonable shapness even wide open. The only let down to it I find is it doesn't feel 'right' if using it with manual focus as it feels a little 'vague' I guess maybe the word I'm looking for......