Climbing shoes function to hug the foot, provide support for the sole, squeeze all the toes together, and allow the toes to push off strongly against a foothold to launch the body upwards. Shoes with soft rubbers provide sensitivity, allowing the climber to feel the texture of tiny footholds wherever the toe part of the foot is placed. Stiffer shoes do not allow the foot to feel the shape of footholds, but they provide support for the foot overall, so one can stand on tiny edges on the wall. Advanced climbers prefer soft, downturned, asymmetrical, tight-fitting shoes, which crunch the toes, pull them towards the big toe, and turn a climber's feet into a claw-like structure that can stand on tiny edges even when upside down in a overhang ceiling structure. For intermediate climbers whose feet are not yet used to modern foot binding, a stiffer climbing shoe which support the feet may be a better option. For beginner climbers who are not used to shoes fitting like a glove, a less tight fitting shoe with a stiff but not too stiff, somewhat sticky, flat sole could work.
I had no clue I would be owning so many pairs of climbing shoes when I started climbing. The problem is, I have what is known as "Greek feet", meaning that the second toe is longer than the big toe. I also have bunions, where the big toe pushes into the other center, and the base of the big toe pokes out as a big bump on the inner side of my foot. Therefore, the front part of my foot is quite wide and the toes themselves are long. This just seems like a bad combination for climbing overall. I mean, if the toes can function like fingers and grab tree branches/foot holds, then my climbing would be great. But since I am a human being rather than an ape, the hand-like functions of the toes are not longer valid. So the length of the toes just serve as a weakness.
My first pair of shoes (La Sportiva Tarantulace) had a stiff rubber sole, did not hug the feet much, and was the least uncomfortable out of all the climbing shoes I tried on. After I got to 6A/6A+ level, I wondered if an intermediate shoe would help me climb better. So I purchased a pair of Scarpa Vapors, since the internet reviews all claimed that this was the most comfortable intermediate shoes available. The fit of the shoes were fine, and seemed more comfortable than other intermediate/advanced shoes I tried on. However, when I climbed in them, they hurt my feet at the big toes from the beginning, and never really got better. The plus side was that Vapors use XS Edge rubber, which are much stickier than Tarantulace's FriXion rubber. The toe box was also pointier, which allowed me to be more precise with my footwork, and my feet slipped off the footholds less frequently. This helped me advance through 6A+ to 6B. In the mean time, I also learned to have better footwork in my Tarantulace shoes (need to push harder into the wall/footholds).
Having experienced a lot of pain in the Vapors, I decided to find another pair of more comfortable intermediate shoes. I landed on La Sportiva Finale (with XS Edge rubber), which are touted to be not completely beginner shoes, but are supposed to be quite comfortable. Unfortunately, they did not perform as well as the Vapors (hug/support my feet as well) AND they hurt my toes.
Finally, I turned to La Sportiva Mythos, which are supposed to be the most comfortable climbing shoes. Now that I got used to Vapor, which hugs the feet much more than the Tarantulace, the Mythos felt much more comfortable than when I first tried them on. Mythos have XS Grip2 rubber as the sole, which are sticky, but less stiff than XS Edge. People with fantastic footwork should be able to climb up to 7A with them. But with my problematic feet and toes, I would feel quite insecure climbing 6A+ and harder with the Mythos. So I would switch to Vapor when I climb a new 6A+ or 6B route.
Since there are no shoes more comfortable than the Mythos, I decided to go for an advanced shoe -- the Scarpa Instinct, which are more downturned, but better made than the Vapors, so they hug/fit the foot much better and provide even more precision. They felt totally fine at the shop, but -- you guessed it -- they hurt like hell when I stand on my toes on the wall. I am still in the process of breaking them in, so I can climb about 1-2 routes with them each time I use them before my toes scream "NO MORE CLIMBING FOR TODAY". The good news is that, comparatively, the Vapors don't feel as painful any more!
You might be thinking what a waste of money! Not quite. Climbing shoe rubbers get used up within 3-9 months anyways. You can either resole them (change the piece of rubber at the toe box), or they would need to be replaced (due to a hole forming at the toe part of the shoes). So far I have resoled my Vapor and my Tarantulace. I will be alternating between all of my shoes for the next few years until they are not resolable any more. I use my Mythos for warm up and then switch to the Vapor for hard routes. I think the Finale and the Tarantulace can be used for outdoor climbing, as well as when the Mythos need to be resoled eventually (takes 4-6 weeks before I get them back). I am hoping my feet will eventually get used to the Instinct VS lace, which is supposed to be a "comfortable" super performance shoe. I now understand that when climbers say "comfortable", they mean that the shoe doesn't cause permanent bruise marks in various spots in the foot. Since climbers often size their shoes down 1-4 sizes compared to their street shoes, by sizing down my shoes only 1/2 a size, by climbers' standards, I might as well be climbing in a pair of Crocs. In the mean time, I will keep toughening up my toes until they get stronger or got completely numb!!