Tamron vs Sigma?!

I'm looking at buying a new 24-70mm lens for my canon 60D.. Unfortunately I can't afford the Canon 24-70mm which is priced at over £1000 :( I'm trying to decide between the Sigma or the Tamron?? I've used a Sigma lens before and the quality was good and I enjoyed shooting with it but I've had no experience of Tamron? 

I'm pretty new to the photography scene, I'm desperate to learn and want the best for my budget.. If theres any photography moguls out there who can help me with this please get in touch!!..