Putting wheel performance aside, i'd recommend going with Logitech for the better customer service. Fanatec are a relatively small company and have had issues with customer service in the past.
Then it depends on what you feel you will do with the wheel. I was unsure whether I would use it for serious online competition (Beyond GTAcademy), so I bought a G27 as it's capable of sim racing with it's decent pedals but still cheap enough to justify the cost as a toy for GT5. A DFGT + CSP would be a good match up if you can get it for cheaper, though I think you need an adaptor.
Or, wait until the G27 goes out of production in a couple of years and the price will fall as places clear out old stock, as happened with the G25 a couple of years back, where you could easily pick one up for £130, less than twice the cost of a DFGT.