depends on the cost and what you want it to do, an imac will be faster id gess.
(depends on model
but any new 4 core+ will beat a single cpu macpro id gess in most tasks)
it gives you the options of internal drives,cpu,ram and maybe swapping the gpu if needed
macpro has a slower cpu,bigger,nosier, sata 2 speed limit on internal drives, no usb 3 (without pci card) no thunderbolt,
imac will come with a new SSD+gpu (macpro may not so if you need them added cost), imac has nice display, imac has good speakers
if you say apps you want to run or which cpu/gpu it has i can say more
both ways you want 16-32gb of ram (id gess)
so if you do compare them add the upgrades the macpro may need to the total cost compared to an imac, also a macmin may work fine for you if your only doing light work
(dont forget to add the cost of display etc if you need them)
