I shoot quite a lot with a Rolleicord V and I love it to bits.
Sadly it's the only Rollei I own at the moment although j might be getting my hands on a Rolleiflex 2.8D soonish.
The big thing with either is condition.
Make sure the front lens board is solid, you don't want it to wobble from side to side at all. When you rack it in almost completely the gap around the edges should be even, not greater one side.
It should sit on a flat table without wobble and the back should fit close and even with no gaps.
These are all faults I have personally seen on secondhand examples that have been roughly treated in the past. Rollei assembly and fit/finish were outstanding. Paint worn off the corners or scrufffy leatherette won't hurt it as a camera but the others will.
Next, if it sticks on the slow shutter speeds, with a second maybe taking five or more, or even needing you to lightly tap it wih your fingers to encourage it to run down, don't freak. The Compur shutter is a fantastic ok'd thing and very reliable. If they are stuck in a closet for years though the old oils will gum up and it will go sticky.
WHATEVER YOU DO DON'T PUT WD40 IN THERE TO TRY AND UNSTICK IT!!!
it needs the old gummed up lube cleaning out and new lube of he proper type put in the rights spots and those spots only. Not a very hard job if you know what you're doing but not a walk in the park either. Best to budget for a CLA then negotiate like hell on the sticky shutter...
As for Cord vs Flex, the Flex has faster lens, lever wind, slightly easier controls but the Cord is lighter and more compact, and it's rarely that you would use the f/2.8 of the Flex lens anyhow. Having to cock the shutter manually is no big hardship either.
Make no mistake, given a choice at the same price and condition I'd go for the Flex, but the Cord is the best bang for buck.
Lenses on either are superb, Tessar or Xenar.
I have several friends with both types and nobody has had any complaints...