Hyd or Mechanical Roller?

There is limited oiling of most solid roller lifters and higher spring loads required. The rollers are oiled by splash off the crank. So extended low rpm can overheat the axles causing failure. Also, the valve springs get hot when cycling and the oil to the top end helps cool them. Less rpm means less top end oil too. So the springs tend to wear out and weaken faster. Any valvetrian failure can lead to the lifter jumping out of it's bore causing oil pressure loss to the mains without oil system modification. These are race parts that can live on the street if carefully chosen. But IMO there is little need for them in most situations. The issue with hydraulic rollers is the same as solid in terms of lost oil pressure due to lift (so a smaller base circle needs to be considered or at least careful checking of the lifter/bore relationships at max lift) and hydraulic rollers are limited the same way as hydraulic flat tappets in regard to lift rate and spring tension.