Here are some of my experiences with different belay devices.

• ATC: an ATC is always a good option, and is great for both lead climbing and top roping, and you can repel with it. Simple to use, light weight, no hassle. For multi-pitch or other reasons to belay from the top, you probably want a guide ATC. I use the one from Black Diamond and am quite happy with it. Not much more to say here.
• Grigri: I bought a Grigri when one of my climbing partners at the gym started hanging for long periods of time on hard problems. I think I have a Grigri 2. It’s great for top roping, especially if your partner likes to hang on the wall. I hate it for lead climbing. A lot of people use it for both, but I cold never get comfortable playing out slack fast enough. On top of that, lowering is a bit tricky and annoying. You get used to it, but it’s never ideal, and it takes a while to teach someone new how to use one properly. They are also bulky. I still use my occasionally at the gym, but less and less.
• Clickup+: The Clickup+ was supposed to be an improved version of the Clickup which was supposed to be a cool new idea in belay technology. I was looking for something for the gym that was equally nice for top roping and lead climbing. The Clikup+ was easy to use, and lowering was super easy with it. The autolocking worked nicely as well – too nicely. It had a tendency to lock when I was playing out slack fast to a lead climber. Got so annoying that I finally sold it. Did not live up to it’s hype.
• Black Diamond Pilot: This is my latest gym device. So far I am super happy with it. Equally easy for lead climbing and top roping and great lowering action and good autolocking. Light weight and and intuitive. Right now this seems to be what I’ve been looking for. I use it with a Magnetron Gridlock carabiner, which I am also super happy with.