This ^^ absolutely !
"The Fanatec allows you to adjust settings on the go" -> is very important. so you can change on the fly (while actually racing) the degrees of rotation and so you can easily find the right setup for your personal taste.
If you want to drift with the G27, I can tell you by experience, the G27 does not turn back fast enough because of this 900°... It is much easier to drift in real life because the feedback IRL is so much better than that of the G27 while drifting. (While normal/clean driving/racing and even a bit on the edge of the limit it is very close to the real thing with the G27)
When racing with the formula GT for example, you can not correct the oversteer fast enough with the G27...
I own the G27 and regret it. I bought the G27 for the 3 pedals and the H-Shifter but I only use 2 pedals and the paddle shifters.
The G25/G27 and even the T500 are good wheels, but I would go for a fantec wheel because only with a fantec wheel you can adjust the degrees of rotation of steering in GT5.
If you drift it is better to have less degrees of rotation.
You said you practically mastered drifting with the DS3? I suppose you use the analog stick for turning. So you are used to being able to switch form full left to full right in a blink of an eye, imagine this with 900° of rotation...