From what I've read about the development of the player, a lot of people liked/loved the version 1, with the main complaint being that it had sharp corners. The v2 was released with a case that had rounded corners and I believe some slightly different markings on the volume buttons, as well as a newer version of firmware that fixed a couple small glitches, and the firmware was backwards compatible with the v1 since the hardware is the same.
The Benjie T6 is the same player with a different brand name and slightly different firmware but you can update it to the Agptek firmware if you want. Benjie is the OEM, Apgtek just rebrands and distributes it for the US/North American market.