This is not so much a question about which is best but a question about which is best for you and how you drive. Some customers want an engine that they can turn 7000 to 8000 rpms so they will need a solid flat tappet or solid roller for that in most cases. Some customers do not want to ever check the valves and do not want to turn their engine over 6500 rpms so the hydraulic roller is a good deal for them. I think we can all agree that the hydraulic roller makes more power than a hydraulic flat tappet.
I think the original post was on a hydraulic flat tappet verses a solid flat tappet. If that was the case the solid flat tappet will always rev higher. We have been cheating up hydraulic flat tappet for years in NHRA racing to turn the engine higher. You can take the hydraulic flat tappet with thick
oil, lighter valve train weights and the right lobes and get them to turn about 7000 rpms. I am not sure what was used in the first posted engine but it either did not have enough spring pressure,
oil pressure, thick
oil or to radical a lobe for the hydraulic because most will go at least 6000 rpms before they take a dump.
No winner in this debate because there is a place for both. You or your engine builder will have to decide this. When you do a lot of engines you look for the best parts for the best prices that will give the least amount of trouble taking into account that the customer will do little to help other than change oil every now and then. You try to recommend certain oils to use but you never know what happens after the engine leaves the shop. Good luck to all and hope you have a great new year.
Thanks, Keith Craft