Blimey! Just got back from riding and all I can say is thanks for all your advice and recommendations - still considering which to go for but this post has been a wealth of information. Thanks
My horse has a spavin and stiffness. The vets said a few yrs ago I'd be lucky if he was even a hack. Now he is out competing in dressage and free as he has ever been. He is on Extraflex HA (the optimum dose not the maintenance dose)- I do believe it has made a remarkable difference to him. He used to be on Cortaflex liquid and then Cortaflex HA but I was not convinced it made too much difference to him. What I would say is that the HA seems to have been key to helping him. I'm very happy with Extraflex HA.
If you have anyone travelling to America pick cortaflex up there, its soooooo much cheaper. So far I have brought back in hand luggage about 6 gallons of the stuff (obviously on different trips!) We even brought some back from Hawaii!
Personally the stuff is fantastic, i also add cider vinegar in and that also helps too