Gotoh magnum is the best, then next to that is Schaller. Kluson started making Schaller style locking tuners a while back and they're just as good. Gotoh Magnums are a bit pricier and so are Schallers, but lately I've seen the Gotohs in the $55~ range. Gotoh has THE best tuning ratio, never slips, and provides very stable tuning. Fender brand locking tuners seem to come in either a Schaller style (thick button) or a Sperzel style (thin button), and they are very stable and never had any problem with them. I don't know who manufacturers Fender brand, but they're very reliable. I find great deals on them so I use them often. I love the look of Sperzel, but in my experience, they tend to slip a little, and I've had a couple which have stripped on the bushing, so I stopped buying Sperzel tuners a while back. Lastly, I recently tried some Hipshot locking tuners. They're good quality, but a little more expensive. I still prefer Gotoh Magnums and Fender.
On paper, the tuning-ratio is the same, but after building and modding so many guitars, you tend to develop preferences. Gotoh Magnum seems to set right into place when turning to the tuned pitch. Other tuners usually require tuning them down then back up a couple of times to get it just right. Sometimes they slip a little, and that's often either the locking mechanism or the gears. There are times when you have to loosen up a set of strings, tune, then loosen and tune again when you're making adjustments. By the 2nd or 3rd time, the high E snaps. Gotoh and Kluson grab the string well, but don't snap as frequently. I don't know if they use larger size ball bearings inside the tuning peg or what. They just seem very string-friendly.
For me, a lot of time the quality is very similar, so I go with the best deal I can find at the time among the brands listed. I supposed I'd buy Sperzel if the right price, but they're not bad tuners. Planet waves and those cheap Schaller knockoffs are far worse.