Usually i use EOS 700D, the reason being my lenses are mostly EFS and ease of use of menus plus its lighter than the 5D Classic. I use the 5D occasionally when I want to take portraits as I have the 50mm 1.8 prime & the 75 - 300mm telephoto EF lenses as the bokeh in the full frame is more pronounced. The 5D Mark 1 is good but 700D is equally good. Bought the classic as a second hand because of curiosity for the full frame. I have a 500D also which now has to go for repair, the pictures this camera took was very good in fact slightly better than the 700D as pixel size is more in the sensor but resolution is less. The write speed of the classic is comparatively slower than the 700D and the CF card for the classic is more expensive than the SDXC cards. Minus point of CF cards is they have to be handled very carefully when taking it out and reinserting to the camera due to the number of pins they have or else any wrong action will render your card reader useless and your camera back for the adapter replacement which is expensive.
The color science of canon digital cameras right from their inception till now is commendable as is the best in the industry. Ease of menu I suppose no other manufacturer can match.