Panasonic 100-300 or Olympus 75-300 (m4/3) Please Help!!!

I use the 100-300 with an E-P1; and I use it a lot. The OIS is absolutely indispensable, and is probably going to be a factor when using it with the E-P3; people seem to have very different experience with the OMD E-M5 which seems to have IBIS that actually works well.

My only disappointments are with the size of the lens, and the fact that it has relatively slow AF on the E-P1, may not be the case with the E-P3.