G.A.S. Attack: E-M10 vs. A7, or When Is a Body Upgrade Sensible?

So I've always been interested in photography and have especially enjoyed it while travelling, but this past year is the first time I've jumped in to the interchangeable lens camera market. I got myself a cheap open-box Panasonic GX1, which is a last-generation Micro Four Thirds camera. I've had great fun experimenting with a variety of native and adapted lens (thanks, eBay!) and I am generally happy with the image quality I've been getting in good conditions. However, in low light and highly contrast-y situations, I do notice the sensor's limitations in both the ISO / noise performance, and more significantly, in terms of dynamic range.

More noticeable than the IQ from my usage point of view, however, are the body's other limitations.

  • No EVF for harsh sunlight (about half and half to gauge exposure compensation and composition)
  • No focus peaking for manual lenses, so I'm relying on magnified view with a low-res main screen
  • Only 1 main dial (which can be toggled by pressing it) to handle exposure functions
  • No Auto-ISO in Manual mode (really cripples use with adapted lenses, since if I want a minimum shutter speed I need to constantly be fiddling with ISO via push-buttons, since it can't set to a dedicated dial)
  • Grip is a bit on the small side when using larger adapted lenses (an old 800g SLR 75-200 f2.8-3.5 was pretty much entirely unusable handheld)

So while I don't think my camera's IQ is a deal-breaker (I am pretty happy to work around it), the handling is seeming like much more of a limitation. Which means a new body. Which is potentially a whole new kettle of fish, and a re-evaluation of what I can do with my camera.

Leading to my Top Candidates...
1) Olympus E-M10

  • Affordable at $650 new, and will be even more so once it starts to filter onto the used market (I'm sure it won't hold its value very strongly)
  • In-body image stabilization (IBIS) worth 3-stops (!) that works even with my primes and adapted lenses, which is a huge bonus
  • 2 well-placed command dials
  • High resolution main screen, decent EVF, focus peaking
  • Nice big removable accessory grip that's only $50 for when I want to use big lenses, but I can take off for more casual shooting
  • About 1/2 stop improved ISO performance, and 2 stops (!) of dynamic range at low ISOs

2) Sony A7 (not S or R)

  • More expensive, but surprisingly affordable on the used market - $1200? (losing value fast)
  • Really nice grip and lots of nice manual controls that I liked the feel of - solid ergonomics, I think
  • Ability to use full-frame lenses with no crop factor - nice for wide and normal focal lengths, but bad for telephoto and macro
  • A lot of "average" full-frame legacy primes in the f/1.8-3.5 range are very, very affordable, quite compact, and will yield much better results on FF than M4/3 (especially with the crop)
  • Good focus peaking and EVF, should be fun for manual lenses
  • 1.5 stops of ISO performance over the E-M10, 1-1.5 stops of dynamic range
  • Really would compliment the GX1, rather than replace it, since there's no option to make it tiny and usable for casual settings like the 20mm f/1.7 pancake, for instance

Am I crazy to be cross-shopping the two? And am I crazy for ignoring APS-C entirely? From what I can see, the very best APS-C sensor (a6000) has only 2/3 of a stop of ISO and dynamic range on the E-M10, and if I'm giving up IBIS at the same time, that seems like a very marginal improvement, and only in shutter-speed limited situations. In static situations I could actually be losing image quality. On top of that, if I need to switch lens ecosystems, it doesn't seem preferable.

I was also looking into Fuji quite a bit, but once I read about all the hassles of working with the RAW files and saw that the super-smooth ISO performance was largely at the expense of detail, it turned me off a bit. I'm also not sure I'm sold on the control logic - that would definitely take some experimenting with to see if I liked it. The native lenses are also neither small nor cheap...

This isn't a choice I'm likely to make immediately (probably will wait until after Photokina anyway to see if that bottoms out the used market a bit more), but I know some of you fine folks have experience with a number of the bodies in question, so I'm curious for any insights you guys might have.