My wife and I travel to Mexico 2-3 times a year and have for the past 6+ years. Protec has historically been our dive shop. (We currently use the dive shop of a former Protec instructor trainer we're friends with). I would highly recommend Tulum over Playa, but of course it's really up to what you want. Here's the reasons:
1) Playa feels like a big city and has alot of hustle and bustle and big city feel. Great if you want ot go out at night and party a little (which you won't because you'll be too tired). It still has all of the mexican street food and flare, but it's just busy. It's not my idea of relaxing. Tulum is laid back, has tons of cheap or expensive dining options to fit all budgets, including street food, is pretty easy to get around (it's become busier lately so not as easy), and generally has a smaller town feel. There's a lot more hippies and Euros in Tulum, but they're all friendly. The feel of Tulum is alot more friendly. There's also a ton of places to stay for cheap, so don't feel tied down to having to stay at Protec
2) The instructors: I greatly prefer the typical instructors that work out of Tulum (though they all move around). Kim is one of the nicest, most professional dive pros I've ever met. He would be my #1 choice, but he is also very busy. It's very likely for a sidemount course you'll be passed down to one of the younger guys (Jaime, Skanda, etc). The instructors in Tulum have changed some since I was last there, so those names may no longer be accurate. Generally though, the Tulum instructors are great and friendly. If you choose Playa, your options are Patrick or Rob. Patrick is an exceptionally nice, amaxing instructor. The only issue is he is super high energy. Like he's on crack and adderall all the time. He's too high energy for me and I don't know that I could keep up. If you're a high energy, quick moving person, then it's fine. I'm more laid back and do things slowly, so he and I wouldn't meld ideally as opposed to other instructors. Now Rob, he's just a douche and I don't feel bad putting it out there because it's well known. He's a well liked instructor, but he can be a real a-hole. My group of 4 friends had a couple horrible experiences with him in Tulum where he acted like an ass to us at the shop. It was pretty bad. The most minor detail being that he removed out stuff from our locker without our knowledge. The more obnoxious detail relates to how he treated the 2 women in the group. I won't go into more detail, but there are many other things with him and they occurred several times. He has caused some problems in his time at Protec. On top of that, he knowingly entered a known closed archaeological site without approval, pissing off many. He's got a big attitude and it isn't a good thing.
So there's my 2 cents. Protec is awesome, especially Tulum. I'm sure you'd be happy at Playa as well with Patrick, but I would say avoid Rob like the plague eventhough I'm sure 50 people will say how great he is. If you ask in the right places, you'll get 50 more that have had the experiences I've had.
