What Pana Lens is worth considering Over Olympus lens if you use OLY body?

Robert --

I have three Panny bodies (starting with the G1) and two Oly's (which were my last two acquisitions).  Since you brought up pricing . . . let me assume that you somewhat interested in that dimension and, actually, would be open to other vendors than Oly.  With that in mind, here's my short take:

• For a mid-zoom, Panny's original 14-45, 12-32 pancake and the newer 14-42 mid-zooms are excellent and a cut above the Oly offerings . . . at the same pricing more-or-less.
• In reasonably priced tele-zooms i have less experience: my Panny 45-200 has been a disappointment to me, but that may partially be due to the shutter shock that early Panny bodies were er to. I've not had experience with the others.
• In primes, more or less they are all good BUT for cost-effectiveness (but not, sadly, size or aperture) consider the Sigma f2.8s.  Their 60mm f2.8 is one of the absolutely best m4/3 lenses available.  Both the 19mm and 30mm are not slouches either.
• It is pricey but the $900 Oly 12-40 f2.8 is a lens for the ages; it unfortunately is awfully big too, but Lordy, what images.
• I don't shoot all that much tele anymore, but since you have an Oly body w/IBIS consider doing what i do:  using a MF film lens and an adapter.  I use the Metabones speedbooster with my Nikkor 200mm f4 and it is perfectly satisfactory as a 280mm equiv f2.8; yes, MF but that isn't an issue for my work/

Good luck.