I recommend trifexis to all my clients. Besides the cost it's a very safe drug. If you see any side effects (e.g. tremors, vomiting) then best to switch to something else. I've seen some vomiting but no tremors. Probably have prescribed it to hundreds of dogs.
I've never used Adequan for management for feline arthritis but physiologically it makes perfect sense. Adequan isn't technically a drug (more of a supplement) so besides the cost associated with the injections there isn't a big downside to trying it out. Also consider using Cosequin for cats...