You'll
need a fast enough SD card for any of the NEX models since their built-in flash memory is good for applications only on the 5R and 6, and nothing for everything else for the moment.
As for MFT,
here you go!
Let me sum it up for you now, as NEX's E-mount and MFT are the two systems that are worth considering right now.
Things to consider about E-mount:
- Higher potential image quality (APS-C sensors are great)
- If you're seriously into video, you can get an E-mount camcorder (Handycam or NXCAM) later on and reuse your current lenses.
- Focus peaking and MF assist comes in very handy when you want to tweak focus in manual focus - or when you're using a manual focus lens, or non-electronic adapter.
- Sony EVFs, if you can get one, are very good. XGA OLED EVFs are awesomesauce. (They come standard in NEX-6 and NEX-7, and you can get it as an accessory for the NEX-5N and NEX-5R.
Things to consider about MFT:
- Potentially more compact (MFT lenses can be smaller than equivalent APS-C lenses)
- Bigger lens selection (MFT's being around for far longer)
- Olympus models use sensor-shift stabilization, so any lens attached will be able to benefit from image stabilization.
- I'm pretty sure that most MFT cameras have a standard hot-shoe.
Remember that both are mirrorless models with a short flange distance - you can adapt a lot of legacy and DSLR glass on them with the right adapter.
It's probably a very good idea to check for online reviews for what you're getting, and if possible, get a hands-on.