Both are good. Don't just rely on hills though. The last marathon I did, I did all of ,my long training runs on the coast path (it's pretty hilly round heree) to try to protect my slightly dodgy knees from the pounding on roads. Although I did all the long runs in terms of time on my feet, the fact that they were so hilly meant they were a fair bit shorter, and I paid for it on race day.
You can view maps for free on the OS site - use the Getamap service, you can even plot routes on there if you like. There are lots of extra features on there if you want to pay for them, but for working out where you want to go it's absolutely fine for free.