I found these thoughts from the Vuurwapen Blog very rational and well stated. Keep in mind, this is written by a guy who served in the Marines. I agree with the sentiment, when you take a shooting class you should be focused on learning how to shoot better. The instructor that can best do that is the right one for you. Who that is and what sort of class depends entirely on your experience and skill.
I've taken basic shooting classes and tactical classes. I've found value in both. However, if I had taken a tactical class when I was a new shooter it wouldn't have done me any good. I both needed to have mastered the basics and developed solid shooting habits before a class like that could be of value.
Last month I attended a class where the total round count for one day was something like 600. This was a pistol and carbine course, and I have reasonable pistol and carbine skills. If I hadn't already has experience with moving and shooting, performing reloads under pressure and clearing jams, I would not have gotten much out of the course because I'd be focusing on those things. I needed to already have those things mastered to be able to learn the new things they were teaching.
Next month I'm planning on taking a basic shotgun course where the round count will be less than 40. Over 8 hours. That's a lot of classroom time and running drills with unloaded shotguns. It's the appropriate level for me because I don't have any practical experience with shotguns. Throwing a bunch of shot downrange isn't going to improve my skill right now. If I instead signed up for a more involved shotgun course I wouldn't get the most out of it because I hadn't mastered the basics. I'd be struggling with tactical reloads while the rest of the class already had that down and was working on other skills.
I guess my point is to not be wowed by somebody with super bad-ass credentials. They may have served two tours in the sandbox and have been a squad leader with 50 engagements under their belt. But being very good at war and being a good instructor are two different skills. Some people have both and some people don't. I have great respect for the guy who served his country with distinction. I also have great respect for the people, both civilian and military, who are good firearms instructors. The second person is who you want as an instructor.
For basic classes I recommend the NRA courses, they have a good instructor training program and are widely available.
Two outfits I can recommend based on personal experience for more advanced courses are Milcopp Tactical and Movement to Contact Tactical. Don't judge either by their website- these guys are very good trainers, not webmasters. A slick website only tells you how much money or time a company puts into web development, not how good they are at their business. It's easy to forget this today.
Good luck out there!