Longer answer is I think it's quite cool to be able to not have to serialize/deserialize everything within telescope, so you can pass around objects (a.k.a. lua tables) that have function references, etc. that allow for very fun extension of the general API.
Another part I guess is that every part (that I have been able to think of thus far) is customizable. So you can change (per-search) the sorting algorithm, the display, the highlighting, the preview, the search text, etc. So you can fine-tune each aspect of it for the particular search or just your general preferences.
Also, I made it just because I was having lots of fun with it. I think fzf is a super awesome application (and plugin), so if it's working well for you I don't think I would switch!
Yeah, these all seem like power-user features for people that want more customization options, and I've more recently reverted to a simpler config with only the most necessary customization. I'll give it a proper try next time I redo my vim config!
Yeah (and I've said this elsewhere) I think people should use the tools that make them productive! So if that's fzf (or something else) then keep using that.
I honestly just made telescope for fun on stream to start with to explore some ideas about fuzzy finding that I thought would be fun. It just happened to be that people liked it and it grew.
We have a pretty active gitter group & people hanging out in the issue tracker, so feel free to ask questions there!
For me personally, it's the coming together of a bunch of things that make it better, I'm not sure I can think of any one thing it does so much better than all competitors rather than just be a very good all-rounder. Maybe ease of code-level configuration counts, (e.g. replacing a function with a custom bit of code as part of "configuration") but not really a "feature" as such.