The Panasonic Lumix GF1 and the Olympus PEN E-P1 currently occupy a unique distinction: as Micro Four Thirds compact cameras, they are the only two cameras of their class today, so if you're looking for one, it's either one or the other.
There's no doubt that the Olympus PEN E-P1 is a stunning looker of a camera, distinguishing itself not only from the GF1 but also most other cameras with its unique retro body. At the same time, while the black GF1 looks inconspicuous, the white and red models are more fashionable.
The Olympus PEN E-P1 and the Panasonic Lumix GF1 are approximately the same size, although the GF1 is slightly lighter by around 50g. The overall weight will change though, depending on which lens you have attached.
Judging from the camera body alone, the E-P1 suffers from an uneven heft. Its weight leans towards the left (the side away from the shutter release button), and it's a camera that really needs to be used with both hands. The GF1 has a more balanced heft that you can easily shoot single-handedly with.
While we were reviewing the Olympus PEN E-P1, an Olympus engineer informed us that the flash was left out to keep the camera as compact as possible, and we wondered if that might have been a limitation of Micro Four Thirds technology. With the GF1's similar size, it appears that it doesn't have to be so.
Olympus also mentioned that flash isn't always necessary, especially with the high ISO settings and low noise performance of the EP-1. While that may be true, there are shooting situations that just call for a flash (ever been at a scene with zero usable light?). While Olympus offers an optional flash attachment, Panasonic's GF1 has one built-in.
And if you really must have one (although we found we would rather do without this time), Panasonic offers a real live view finder attachment which feeds from the sensor, while Olympus only offers a glass view finder attachment that isn't connected to the sensor feed at all.
The E-P1 had problems focusing in low-light situations (Olympus has just released a firmware update which promises to improve the auto-focusing, but we haven't yet tested it), but in our experience the GF1's auto-focusing is faster and more accurate.
Since we didn't have an E-P1 on hand to simultaneously compare the GF1 against, we decided to leave a more comprehensive performance shootout to later and just use the test footage from our previous E-P1 review for a quick comparison overview.
Since the E-P1 doesn't have a built-in flash, it relies on its high ISO sensitivity to capture light. While the E-P1 goes up to ISO6400, the GF1 goes up to only ISO3200. From our ISO chart comparison, we found that the E-P1 has better ISO performance, with finer grain and lower noise than the GF1. Both cameras' images at ISO1600 are still usable, but at ISO3200 the GF1 is noticeably nosier than the E-P1. At ISO6400 (not pictured) the E-P1's photos are too noisy to be usable.
Video shot with the E-P1 and GF1 are both good quality, but the E-P1's kit 14-42mm f3.5-5.6 lens produces more noticeable noise while auto-focusing than the GF1's kit 20mm f1.7 pancake lens.