wouldnt ms grease do the same job?
Basically, ANY grease is always better than NO grease.
After that it's a question of degree - and sometime good judgement.
For example, I know of a case where a guy was stuck in a petrol-engined vehicle, due to a holed sump - ALL the oil had run out. He fixed the hole with some sort of epoxy putty stuff, but had no engine oil. He filled the sump up to the mark with diesel fuel. Not great as an engine oil, but a thousand times better than NO oil. The vehicle was driven out, about fifty miles. Sump drained, new pan, filled with proper oil, and that was that - no harm done. And yes, it WAS a LandRover, an army one, low compression head, and was driven gently till it reached safety. The oil light stayed OUT all the way, so he told me.
In molygreases, the thing is to find out what percentage of MoS2 (molybdenum disulphide powder) is used in the grease. As far as I know, Castrol MS3 'Moly grease' is about 3% MoS2 added to a lithium based grease. This will make it a very good grease for all general uses, and maybe even some extreme appliications. Rocol MT-LM is not meant to be used as an ordinary grease, being 60% MoS2. It is intended as an assembly paste, to provide maximum protection of vulnerable moving parts in the first seconds of starting up an engine or machine after a build or rebuild. Then the residual moly mixes into the general lube oil and helps things along.
UJ's are different. There's so little space in them, and no way normal greases can "flow" as they will in wheel bearings. So, the best lube is the one that can deal with the worst excesses, and that's where Moly comes in, and the more the better.
Castrol MS3 will do just great in UJs , and better than any ordinary yellow general purpose grease. It's just that a blob of Rocol MT-LM might do a bit better when you assemble the UJ, after which you grease it as normal.
The great thing about Castrol MS3 is you can get it into a grease-gun. MT-LM doesn't like that idea. Like me, it's too thick.
CharlesY