New Mini or older iMac

Just looking to get back into macs last one i had was a mac mini just as the intel ones came out.

SO been looking at the mac mini i5 or a 2nd hand core2duo 2.8 /3.0

Is there much in these from a spec point of view?

All i am planning to do is general usage / graphics work as in logos vector work / no video encoding ?

Would the imac last as long as the mac mini?

Go with the new Mini. It's much more powerful than the older iMac and will certainly last a lot longer. Of course that does mean you'll need a decent monitor and keyboard - mouse.