Well, I can't comment on the G-27 yet, for I don't have one, but I have a G-25 for almost two years now, and I must attest the G-25 is a solid and reliable wheel, for just about any kind of racing you prefer.
If you really like racing as much as I do, and you want to race online in various Sims Racing Series like Nascar Sim Racing, ARCA ReMax, R Factor, on different organizations that have the Nascar Cup, Nationwide,or lower series right down to Modifieds, or even Formula 1, and there are Hundreds of the organizations online that require a membership, you better have a good, decent wheel (NO JOYSTICKS). Most won't let you race or become a member if you don't have a wheel. Even the real life NASCAR drivers race in these online series, for practice or prior to their upcoming weekly event.
I'm considering one of the G-27's, but right now I couldn't be happier with my G-25. While racing online, I prefer the paddle shifters to the stick shifter, whether it be on a oval or road course, to where it lets me keep my hands on the wheel than worry about distracting me to shift, plus not worrying about a shifter when you have to downshift say from fourth gear to third gear and accidently throw it into first gear resulting into a blown transmission or blown motor.
And the cost of these units, the G-25, G-27, or others listed here in the forum are not that bad in price or outrageous on price as stated. There are others that manufacture wheels for true diehard online racers like me who like this, like the Thomas Super Wheel(www.thomas-superwheel.com) and ECCI (ECCI6000.com), and I'm seriously looking at a TSW right now. But get ready to spend some bucks if your serious and like this as I do.
Logitech makes a good wheel, so if you really want to see how good you are as well as the wheel, get online and race with about 30-40 others and that will tell you how good these wheels are.