For me the best one to use long term is the one they will reliably take!! Most are given daily as either a tablet or liquid but some are given less often (monthly in one case).
It can be a case of trial and error to see which suits your dog best.
Like Lynsey said, regular check ups and monitoring are important with any dog on any long term drug.
I don’t believe there is a superior NSAID *mad* The problems seen relating to liver/kidney function are if there is already a problem with either organ or a condition develops affecting those organs. Then the NSAID may exacerbate things and your vet may consider continued use or reduction in dose.
Any dog receiving NSAIDs should be monitored with baseline bloods, and then around every 6 months to make sure that there are no developing issues which may affect the usage.