I'm quite certain that someone who has decidedly a preference for the Leica-look will be unhappy with Olympus lenses. As far as I've learned, the Zuiko lenses deliver (too) much contrast, and have on the other hand less resolution than the Leica lens user will demand.
The Olympus Zuiko 90mm f2 and Leica Summicron 90 f2 look to be comparable in contrast and resolution in these test from Modern Photography:
Leitz 90mm f/2 Summicron-R (1978 era 3-cam)
Leicaflex with mirror and diaphragm prefire
Vignetting = B @ f/2, A- @ f/2.8, A thereafter
Distortion = slight pincushion
Aperture Center Corner
f/2* C+ C
f/2 B B
f/2.8 B+ B
f/4 B+ A-
f/5.6 A A
f/8 A- A-
f/11 A A
f/16 A B
Notes: * = Tested with a B+W 010 filter. Moderately high contrast images at f/2; high contrast images at f/2.8 and f/16; very high contrast at f/4 and f/11; extremely high contrast images at f/5.6 and f/8. Lens condition 9+ (KEH=Ex+). Paired SQF grade and contrast comparison to the 90mm f/2 Zuiko Macro test done on a OM-2000, with SQF differences
significant at the 1/3 grade level.
90mm f/2.0 Zuiko Macro (multi-coated)
OM-2000 with mirror and aperture prefire
Vignetting = C+ @ f/2, B at f/2.8, B @ f/4, A- thereafter
Distortion = none
Aperture Center Corner
f/2 B+ A-
f/2.8 A- B+
f/4 B+ B
f/5.6 A- B+
f/8 A- A-
f/11 A- B+
f/16 A- B-
f/22 A- B-
Notes: Moderately high contrast images at f/22; high contrast images at f/2, f/2.8 and f/16; very high contrast images at f/4, f/5.6 and f/11; extremely high contrast images at f/8. Paired SQF grade and contrast comparisons to the Leitz 90mm f/2 Summicron-R test done on a Leicaflex, with SQF differences significant at the 1/3 grade level. Condition: 9+ (KEH=Ex+).