M42 vs M44 head

[halcrontech]

I am wondering which head is better for around 8000 RPM. M42 head using flat lifters or M44 using roller rocker arms?

Only the surface, the roller arms used on M44 seems superior in terms of performance and friction compared to M42 flat tappet. But how about real life application? Is it well designed for high RPM or is M42 head better suited for high RPM?

Btw, if M44 is better, can I put M44 head onto M42 motor?