Ive been using our 2x for a good 6 months now and I can tell you it's a lot more finicky than the rep 2. Dual extrusion is still somewhat experimental but CAN work depending on what you want to do with it. It requires some changes in the CAD design process in respect to planning how things will be built. It is VERY temperamental, but after you've been using it for a few months you get a feel for its quirkiness.

You CAN print PLA on the 2x but the results I have had have been less than desirable. I think it might be due to the fact that you cannot manually set the LOAD/UNLOAD temperature and the PLA heats, maybe a little too much.

There are a lot of reason you might want to use ABS or other types of polymers other than PLA. PLA is nice and pretty, cheap, and smells good when you heat it up but it is very brittle and has a lower melting point than ABS. ABS has a higher melting point and is more flexible. You can also use things like HIPS (see the new dissolvable filament), nylon, pva, laywoo, etc.

If you just want to have fun printing things go with PLA and the rep2. If your feel like getting your hands dirty or doing this as a business you might want to try the 2x.