That is a debate that will go on long after we're dead and gone....lol...the manufacters will tell you yes, personal proof of JUST the friction aspect...no. ( to be fair, I've never JUST taken a set if ductiles for example, and then swapped JUST for a roller rocker set on the dyno) That being said, what typically happens, is you get a better rocker, with better RATIO and then the answer is yes. Sometimes substantial. When you play with stock eliminator stuff, class engines etc, it really becomes apparent, as well as bigger inch motors where the higher ratio camshafts are used. I'm going to end my answer there, because everytime this comes up, there are 9,000 naysayers that have some sort of negative comment to make about " better " rockers, and they lack of value. Simply not the case, but I'm tired of arguing it for 25 years....lol...there is also reasonable argument, as to WHEN do you need a better rocker arm. Most street cars simply dont care. When a guys says " Iv e been running them for 15 years without a problem", that means nothing to me.How many miles has it ran, how many passes has it made, how many RPMS has it sustained, how much spring pressure does it endure and so forth. Years mean nothing unless there is data behind it. What most good rocker arms DO do, that many others dont, is keep the valve guides and valves from side loading, and wearing out the valve guides, which in trun makes the valve job worse, which hinders valve seal etc. Thats what many forget. Also, there is a huge difference between older rockers, and some newer designs, as far as rocker tip, and roller tip centering over the valves. Some of the older ones are just WRONG for the newer heads.