Take a look at post 208 or the XBee 3.0 spec sheet, where the model numbers are explained with descriptions. The ones in @vjv's post are identical except for the "-J," which distinguishes non-Pro models from Pro models in the 3.0 series. Both have PCB antennas (the "P" in the model number indicates this).
The non-Pro models don't have an insanely strong radio like the Pro models do, but both should be fine for normal use as a router/repeater. I assume the price difference reflects some difference in the component costs.