Bike noob here. I am biking mainly to help rehab my knee. A friend of mine has lent a mtn bike so I can test out the sport and see if I would like to buy my own bike. I have been looking at bike locks and the Kryptonite brand seems to be very highly regarded, in particular the Fahgettaboudit with its 18mm diameter. But some of the reviews of the Fahgettaboudit fault its 6" tube, claiming it's just a bit to small and limits the ability of items to lock onto and the ability to lock qr front wheel with the rear and frame. Some sites have claimed that the 16mm thick tube of the NY STD is nearly as good as the Fahgettaboudit but the 8" tube makes it more versatile.
I live in Atlanta and have been told that bike crime is fairly bad around here. That being said the bike will be housed inside most of the time but I would like to ride to the gym and occasionally to restaurants. The bike would only be locked for 1hr at a time.
I have read, on this site and others, that two locks is really the way to go but I really don't want to have to carry all of that gear with me. If I only carry one lock I would need to secure the qr front wheel and that is my dilemma. Get the better Fahgettaboudit but not be able to lock the front wheel, or get the NY Standard which would.
I have the NY standard and lock my rear wheel and seat tube to the bike rack. I live in Chicago where bike theft is rampant & still have my expensive bike. It will take at least 10minutes of angle grinding to break either of those locks. I have used OnGuard locks in the past & feel Kryptonite is much better quality. However, Kryptonite is more expensive. I have not used Abus but have heard they are good also.
The NY Std is more versatile, and it's one of the best locks on the market. I would recommend the Std over the F, for your purposes it will more than suffice. Mountain bikes have thicker frames and thicker tires, so the extra room on the Std will be useful if not necessary. Lock it to the back wheel/frame (remember- the back wheel is 2x as costly as the front). You can use a cable for the front wheel. Cables are otherwise useless, but it's unlikely anyone will snip it just to get a front wheel. If you're really worried about the front & don't want to use a cable, get a cheaper, lighter u-lock for the front wheel.
I own both locks and agree with the criticism that the Fahgettaboudit's shackle is too short.
It's impossible to lock through the rear wheel and rear triangle since the bike fills the entire thing. There's nothing left of it to lock to anything. The diameter of its bend could be larger too. It will barely fit around a 4" pole. Of course when you do that, there's only two inches left over to fit the bike.
The NY Standard is a nice size. I can fit the frame, wheel and post through it--most of the time. I have trouble locking to the cart racks at the grocery store with it. Otherwise, it's pretty much my default lock.
As for the wheels, ditch the QRs and get either bolt-on skewers or locking ones. I've got locking ones that include security bolts for the seatpost and headset cap.