Congrats on your G25 Dan. Sounds like you got yours just a week after I got mine, so we're both noobs with it at the moment.
I've found the gear shift an absolute blast to use in the XFG and I don't mind being a little slower because it's worth it for the fun value. I hope that I'll become just as quick in time, I'm having to switch on throttle blip to help.
Because the LRF cars are faster between the gears, there's a little more speed lost using the gear shift. I think I'll be sticking with paddle shift for Road Sport Winter Cup - at least until I'm more familiar with gear shift.
I don't like stick shifting, maybe it's because of the speed of the cars that use it.
In summary; if the fun aspect of using gear shift is outweighed by too much speed loss, I'll use paddle shift. It's all about fun!
Dan - check
this idea out for easily swapping between the modes.