Michael,
There are a few different 3 models now -- NEX-3, NEX-C3, NEX-F3, and NEX-3N.
The NEX-3 and NEX-C3 are very similar, entry-level, and do not support the EVF accessory, and do not have a have a built-in flash.
The NEX-F3 has a built-in flash (same as on the NEX-6/7) and has an accessory port that supports the external EVF. Its screen flips all the way forward, but downward tilt is compromised.
The recently-announced NEX-3N is a new body design, very small, has a built-in flash but no longer has an accessory port, so no EVF. Its LCD flips all the way forward, but there isn't any tilt in the other direction; eg, waist-level is easy, but shooting with the camera above your head is compromised.
The NEX-5 series progresses from the 5, to the 5N, to the current 5R. The 5N and 5R both support the EVF accessory. The 5R adds a faster autofocus system, Wi-Fi support, and increases the LCD tilt range to face forward, but doesn't sacrifice tilt in the other direction.
I own a 5N at the moment, but if I were buying a new NEX today I'd go with the NEX-6. This comes from the point-of-view of someone who rarely uses NEX native lenses. For me the camera is an APS-C back for M-mount and other legacy lenses.
Whatever version you get, I highly recommend the Hawk close-focus M adapter (
http://www.daguerreotyping.com/?p=2112) if you want to use it with M lenses. Adds some versatility to the lenses that you don't get with a traditional rangefinder.