Choose Gaydar if You want a focused dating experience built around profiles, daily matches, verification and privacy, without needing to build your own search from scratch.
Choose Jack'd if You want detailed search, extensive filters and a large Nearby experience with lots of different ways to interact with other members.
Neither approach is inherently right or wrong. Sometimes you want to fine-tune your own search; sometimes you'd rather the platform do more of the matching work for you. You don't have to decide what kind of dating experience you want forever; try Gaydar, see how the community feels, and decide whether it works for you.