My parts guy recommended Lemforder when available, so when I did all of my front arms, it's mostly Lemforder with a few Meyle HD when we could not get Lemforder.

Regarding how many arms to replace, I did the front lowers and the front uppers as sets. So, first I blew a bushing on the upper CA's, and replaced all 4. Then I had a failure of one lower bushing, so did all 4 lowers. This was last year at 90k miles.

Even a seasoned suspension guy may not be aware that the bolts for the LCA's need to be finally torqued with the car's weight on it. Uppers should be replaced one arm at a time, ensuring that the resting heights are equal, if that makes sense.