yes i have both ,to be perfectly honest although the 70d is twice the m/p and 5 years newer in design ,once you have used a 1D3 and processed the files from it your hooked its a really easy camera to set up not complicated ,the RAW files are a dream to work on ,and noise right up to 3200 iso is not a problem ,its there but easily cured if annoying .the battery life is like for ever ..the a/f system is superb and the ring of fire a/f is extremely good in 90% of circumstances .
to sum up get one and i don't think you will use the 70d much afterwards