I do injections as needed, and usually feed GLC 5500 max but  looking to change. What are some recommendations? I'm curious about tight joints plus. 

If I decided to waste more money ... which is more than likely... I'd go with GutX...its geared for gut health but it's a good dose a hyaluronic acid. So I'd hopefully get  gut health AND joint support in one... more bang for my buck! That being said.. I've started all my horses on GutX .. 2 for sure are ulcer horses.. 1 is at the trainer and he recommended we put her on Gutx, he has everything on it that comes in and swears by it. The other is home and definitely had ulcer issues as well. I'm still doing the loading dose on her. She is definitely eating better since we've started it. I just decided to put the other 3 horses on it too. It's not incredibly expensive. I know they have a joint specific supplement available too. But I just decided to use the GutX since that what the trainer asked she be on. 

I have mine all on MVP Exceed, covers all the bases. And has proven to work for me, I still inject but the natural fluid that has come out has changed from watery to the proper thicker/stringy fluid. Once gelding was always dry, you'd never get a drop for years and now he has fluid coming out. The vet I use for injections is super skeptical about any type of feed thru's, but he was impressed by what he was seeing firsthand with my horses. I also cut down their grain after they went on it, they were absorbing the nutrients more since it's for digestive health as well. SO that was an extra perk. The one's not running barrels just get 1 scoop of it daily, my 29 year old moves so much better on it. And if I'm running one, or right now I have one rehabbing KS and stifle surgery, they get the normal 2 scoop serving. 

I'm not much on feed through joint supplements but I've had success with the MVP Exceed 6 way as well.

My vet recommended Equithrive which is backed by science. He said Adequan is the best and this is next. My mare hates needles so this is what I'm using and she's a pretty picky eater but eats it fine. Before talking with him about it (and before she was running) I tried to use exceed 6 way but she wouldn't eat it. I could split the dose up and she's get some but I could never get her to consistently eat the whole dose throughout the day. 

Cosequin

MVP Exceed 6-Way. I have everything from 2yos to an 18yo on it

I have 4 horses and not a one would eat the Exceed 6 in 1.  Half dosed it, nope. 1/4 dosed it, nope.  Had to put so much Healthy Coat in it to get them to eat a half dose it wasn't worth it.   Had mixed results with Equithrive.  Have had the best results across the board with OE Gamechanger Plus.

Myristol Pro

My go to for joint supplement is Osteo-Flex by TLC Animal Nutrition. My horses love it. Comes in pellet form. I also feed Equi-bone by TLC as well. My navicular horse that also has some joint issues is running a 1/2 sec faster & feeling better. On that note.....what works for one might not work for another