The X-E2 is likely the best candidate for switching camps, as it's at that delicate US$999.99 mark, without a lens. The wondrous thing is that this is already a second generation body that has their improved sensor with phase detection and they've included an upgraded processing engine to accelerate response time.
Up against the GX7 and E-P5, you might wonder if there isn't a huge difference. Obviously, with the E-P5, the out-of-the-box difference is that there is no viewfinder, other than the rear display. The VF-4 is an additional US$299.99 but well worth it, as the same unit was put into the E-M1, and I found that to be almost as good as an optical viewfinder (it is near the size of the viewfinder of the Canon 1D x), similar to what's used in the FujiFilm X-T1.
The GX7 includes a viewfinder, apparently the field-sequential type with some rainbow-tearing effect but as I've been told, the problem is minimal. If it eliminates the problem of blackout that I find with the GH3 EVF, I'd be fine with a bit of some rainbow weirdness, as long as I could see something.
I've included the E-M5, even though it's older now, because of the inbuilt viewfinder. In many ways, it's close to the X-E2, e.g. with the 1/4000th of a second shutter speed, whereas the GX7 and E-P5 have 1/8000th as their fastest speed. It also has very good performance in low light, enabling very usable photos at ISO 6400, something that the X-E2 supposedly does very well. Since I started writing, the E-M10 has been introduced by Olympus, which makes this a more interesting comparison since it lacks the weather-sealing that the E-M5 has and brings the price down while adding the TruePIC VII processor for better image quality.
There is some weirdness with the X-E2 (as with all FujiFilm X-mount bodies), as you cannot use raw files and use an ISO sensitivity above ISO 6400--you must use JPEG files. Why? I suspect the only change to this will be in future generations.
Still, I'm betting with all of the casual users in this category, few are put off by having to use JPEG files in many circumstances, especially if they've been using such files from Olympus' excellent JPEG engine. I'd think that many won't want to use a raw development application to process their files at all, even the excellent Capture One by Phase One.
I would consider a few things important in this category:
- Image quality
- Lens availability
Since the sensor size is larger, mobility is going to be affected more with the larger lenses of the FujiFilm system lenses. Sure, they could make smaller lenses (they have the XC compact line), but at a huge compromise to image quality, just ask Sony and Samsung. Even Olympus and Panasonic have made compromises to the lens configurations for the sake of compact dimensions and low weight. That isn't to say that you can't get great photos using inexpensive lenses, but the clarity will probably not be there.
Image quality is where the X-Trans Sensor II shines. Since the colour filter is seemingly more random (that's not precise but it seems a simpler way to put it), the colour should be better. However, most raw development applications are having trouble making the most of it at the moment.
At 16.x MP, all of these sensors are a similar range, but the FujiFilm sensor has the least pixel density, which (all things being equal) should give it another advantage. For the person printing no larger than 4x6 prints or sharing on the web, there likely isn't any advantage, and even the cheapest of these camera makers' mirror-less models will do. (Given the 16.x MP Four-Thirds sensors, the equivalent pixel density would be part of an APS-C sensor with 24.x MP, such as the Nikon D7100 or Pentax K-3.)
Lens availability is becoming less of a problem for FujiFilm and they're bringing some desirable lenses to market, hopefully with some incredible image quality. The X-E2 is especially able to take advantage of the newer lenses with lens profiles, even over the X-Pro1.
The availability is also the reason I would never consider the Sony or Samsung lines to be useful. To be blunt, half-ass is not a great way to do things. Even as another electronics company, Panasonic hasn't made horrible photographic mistakes. They've stopped doing checklist engineering, and they're really thinking about how people use cameras. Sony recently dropped the NEX name, possibly because Samsung copied the name (does NX seem like NEX?), or maybe to integrate everything under the Alpha name. As far as I'm concerned, they (and Samsung) could have used HA as their system name. That's not to say that Samsung and Sony don't make great components to be used in other companies' products--they do. Their products are just less than the sum of their parts.
In all of this, I'm still not sure which camera body I would choose. I think that micro Four-Thirds (GX7, E-P5, E-M5) is very compelling with a solution for almost any situation. However, FujiFilm is giving their system a lot of power and solving a lot of problems that others wouldn't even consider.
If you loved FujiFilm's film, you'll likely love their film emulation modes in the X-E2. If you want a vertical viewfinder, you'll love the GX7. The E-P5 is a better stills photography tool than the GX7 but it lacks many video capabilities, and doesn't include any viewfinder for use in harsh light. The E-M5 is still a quick, capable camera body with more options for better handling of larger lenses than the GX7 or E-P5, though it could use a faster 1/8000th of a second shutter speed. (How did we manage way back when with 1/1000th?)
I suspect that FujiFilm's X-Trans sensor in future generations will be seriously compelling to those using Sony's sensors (or Canon's aging sensors in this price range), as by then the raw development applications will have better processing of the files, and FujiFilm will have ended the ISO sensitivity restrictions. It should already be a worry for Canon and Nikon, but as FujiFilm progresses, what will they do? A few years ago, the FujiFilm S5Pro was quite a camera body with a good sensor for studio use--big dynamic range, great color--but it was too slow to be used outside the studio for anything but landscape. They've come a long way enabling some very desirable, small camera bodies.
Update 2014.12.21: Although the X-E2 has been given enhancements via firmware updates, the camera body hasn't changed. By this time, the GX7 is about half the price of the X-E2. The GX7 doesn't have as good image quality as the X-E2, especially in lower light conditions, but it does video well, something the X-E2 does not do well.
Thankfully, FujiFilm has brought a number of good (and some great) lenses to market, becoming less of a disadvantage of the system--i.e., micro Four-Thirds has a great number of native lenses available, plus all of those available through adapters.
Update 2015.09.14: The Panasonic GX7 has been replaced, as has the Olympus E-M5. While the E-M5 MkII is about the same size as its predecessor, the GX8 is much larger, making it more balanced with bigger lenses. They removed the inbuilt flash and weather-sealed the body, plus gave it 4K video recording capabilities. The new, stronger EVF is amazing (and still able to be tilted) and the rear display is not only so much better but it's also fully hinged, so low architectural shots are now possible.