I hvae used Smartflex Senior Pellets and Cosequin ASU Plus and have found a big difference in the results.
My 26 year old Paint was started on Smartflex Senior back in 2011 and I saw a slight improvement in his right leg stiffness. My veterenarian recommended a gram of Bute before each ride while on SmartFlex Sr. My farrier also asked that I give him the same dose of bute before each shoeing.
I switched him to Cosequin ASU Plus because of the Hyaluronic acid it contains.After a few of months, I noticed big difference. I no longer need to give him bute before rides or shoeings.
Enjoy your ride,