I've been a bit slow on moving to micro4/3 as I have tried to make some sense of the options and alternatives. And I think I'll need to wrtie a post with some questions. Last one was at October, or so..
If there are mistakes, please reply.. I know less of Panasonic models, so ..
Memory cards are the same (SD/SDHD), finally.. Olympus had that stupid XD card way too many years.
Note, there is now a new varient (SD-XC) if you want 64GB cards. I believe the older models did not support SD-XC, but the newer ones should. Similarly there is a new speed grade for SD-HC and SD-XC cards (UHS), and presumably newer cameras support it. (the new generation of Pens do, I'm not sure about Panasonic). If you have an older laptop or card reader, it may not support SD-HC or SD-XC cards.
Lenses seem to be compatible among brands, IIRC there was something about OIS control issues with some lenses at Oly bodies. Of course focusing speeds are different, but final accuracy is close to 100% (Af-S mode at least).
If you have a Panasonic lens with OIS, and there is no switch on the lens to enable or disable OIS you cannot use OIS in Olympus bodies, only the Olympus IS. The older Panasonic lenses had a switch on the lens, but the newer ones do not appear to have it. OIS in the lenses is most useful for video, but it is also useful to prevent the image from jumping around when framing handheld.
If you have a classic 4/3rds lens with the adapter, Olympus bodies will auto focus in S-AF mode, but Panasonic bodies will not AF some lenses, and on other lenses, the compatibility documents say that AF is unreliable, and you should plan on manually focusing with the lens (but it may work). None of the micro 4/3rds bodies with do continuous focusing with a classic 4/3rds lens. Either adapter (Panasonic DMW-MA1 or Olympus MMF-2) will work on any body.
External flashes, when used right atop cameras should work with TTL. But only Olympus has the wireless-TTL control system.
Right. Note, that in addition, Panasonic does not offer any way to disable the pre-flash, which makes it harder to use external flashes as dumb slaves.
Also, note the G-F3 does not have a flash hot-shoe.
External video microphones need different adapters/cables, and not all models support those.
All of the Olympus models, except for the E-P1 support the same adapter (SEMA-1). You cannot use the external flash or external viewfinder when the SEMA-1 is used. The SEMA-1 takes a standard phono plug, and comes with a cheap omni-directional microphone, but you can replace that.
Remote releases and batteries are incompatible. At least Oly uses the one type on all µ4/3 models (bls 1/5), not sure about Pana?
Olympus uses the RM-UC1 on all Pens, except for the E-PL1, which does not support a wired shutter release. Note, without going to a speciality device that has a combined cable, you cannot do both shutter release and external VGA at the same time. Olympus unfortunately (IMHO) make the decision to put the cable connection on the right side where you want to grip the camera.
All Olympus bodies can use the same batteries. There are two varients: the original BLS-1 and the new BLS-5. The BLS-5 has an extra contact that is used by the new charger (BCS-5) to turn off the charger if the battery is full. This is evidently to comply with a law that went into effect in Japan 2 years ago. After the earthquake, there were reports that outside of Japan, Olympus had gone back to supplying BLM-1 and BCS-1 with new cameras. The old BLM-1 batteries cannot be charged in the new BCS-5 charger. I believe you can charge new BLM-5 batteries in the old BCS-1 charger, but Olympus doesn't recommend it.
My impression is Panasonic seems to change batteries with every new generation. Originally they were adding firmware to not run on generic batteries, but I've read they lost a lawsuit, and now share the secret sauce with the generic battery makers.
But how about those µ4/3 acessory port add-ons (like VF-2, MAL-1, PP-1) .. I know that oly has two variants of the port and some add-ons need the AP2. Is the Panasonic port same, DMW-LVF1 looks a lot like VF-2 ??
The E-P1 does not have support for the accessory port.
If memory serves, the only thing that requires the 2nd generation of the accessory port on the Olympus is the PenPal bluetooth adapter. The E-P2, E-PM1, E-PL3, and E-P3 support the second generation of port.
The older Pens (E-P2, E-PL1, E-PL2) needed a firmware update to use the VF-3 viewfinder.
Panasonic and Olympus have different accessory ports.
The E-P3 has an add-on grip that is only usable on the E-P3.
As a general rule of thumb, Panasonic tends to have better video support, while Olympus tends to have better flash support.