Different technology. PyPy/RPython is a more "high level" approach built on top of metatracing while OMR is more low level and geared towards method-at-a-time

Different technology. PyPy/RPython is a more "high level" approach built on top of metatracing while OMR is more low level and geared towards method-at-a-time JIT. (I might be wrong. I worked more with pypy but only know OMR superficially)