The short version is that depending on where you are, every app can have a very different audience. Any one app is not inherently better than the other in terms of finding a hookup versus finding boyfriend material, and in different locations every app may have a different vibe. The only way you will know is to check them out for a while and see how they shake out in your area. Also... surprise! Six months later, the population may have changed and might be completely different.
For this reason, many people are on multiple apps... precisely because you never know where you're going to meet someone to your liking. Some people are lazy and don't want to be on multiple apps... that's fine, but they shouldn't complain that they're not meeting a variety of people.
And all the apps can be for both hooking up and for meeting people for relationships. I've hooked up from "dating" apps like Tinder and OKCupid, and I've had multi-year relationships with people met via "hookup" apps. While some may trend towards being more hookup oriented versus dating, they're all just as valid for meeting people.
The most important rule for apps is that you will get out of it what you put into it. Communicate your interests clearly and you'll be more likely to find someone interested in that. Looking to date? Say it. Looking to fuck around? Say it. But don't make the mistake of writing a novel in your profile... that itself tends to be a sign of a self-indulgent narcissist who doesn't have a sense of the appropriate time and place for an endless monologue. Do share your intentions and you're more likely to find people interested in similar outcomes. It may or may not hit home with the Grindr crowd, but you never know. Again, some pretty significant relationships, for myself and among a number of friends, have come via hookup apps while the "dating" apps were useless.
Also, you should have realistic expectations: You can have a wonderful and rewarding short-term fling. You can have a hookup that turns into a life-long romance. I once met a guy who was moving in 2 months; we had an incredibly wonderful 2 month thing and we remain great friends to this day. We didn't get married, but I wouldn't call that a failure by any means... my life is richer for that experience. I've also become great friends with people who were hookups, so don't discount the value of those connections either.
This leads to a larger point: You never know what you're going to find, but if you don't put yourself out there, or if you are dodging opportunity waiting for some mythical perfect moment to come into focus... you're going to be very disappointed. If you're waiting for the perfect relationship to present itself, and you're dodging possible hookups as a result, all you're doing is just missing opportunities to be pleasantly surprised. Personally, I'm now married to a guy who was a post-divorce casual hookup... you never know who's gonna come for a blow and never go.
Finally, please please please... have a fucking picture! Or at least send one with your first message. If you won't show your face, most people will assume you're some kind of closeted psychopath or otherwise hiding from the world... and that's not attractive to many people. If you're not ready to put yourself out there, figure out what it will take to overcome that and do it. Then you'll be ready.
Cheers!