For me, it's because I can try it out and have the option with the parts I have in my garage. The circumference of the factory fitted 27"x2.35" is 2209mm and 700x40c is 2205mm, room for fitment isn't a problem. Without the mudguards a 700x50c would probably fit no problems at all.I believe G-One is the best tire when it comes to speed/rolling resistance for its size. I don't understand why people in this thread are constantly trying to change a perfectly good tire. Even in Schwalbe's website you can see that G-one is among the best , if not the best, when it comes to rolling resistance/performance so by switching to a different tire you will almost certainly not gain range but lose some.
From the photos of Quick-e there seems to be little clearance for 700c wheels and even if you can fit 40 tires it will have most likely more rolling resistance and you will loose a lot of vibration dampening with the baloon G-ones.
The only problem with G-one's are their durability. Imo you guys should first wear your tires out then you can switch to a marathon series tire which is very durable although not as efficient...
When I get around to trying some different wheels and tyres out I'll post some pictures.