I've owned one of each generation OBW since 97, and all were H4 LTD's, and each one was better than the last one. If I were in the market in your stead, I'd spring for the 3rd generation. Two things stand out for me.
The 2nd generation didn't entirely get the headgasket issue fixed that haunted the first generation engines. While they no longer blew out with the same frequency, they did however, leak small amounts of coolant to the OUTSIDE of the engine on some cars. In my case, the coolant never made it to the ground, but you could smell the coolant in the car when it was parked over night. Subaru even had a special coolant additive to help fix the problem after you changed the head gaskets. My 2004 required the warranty fix at about 23 000 km.
The 2nd generation OBW's needed to have the rear head rests removed from the seat tops before you folded down the backs to allow a larger cargo area. In the 3rd generation OBW you simply just flipped the seat backs forward, leaving the headrests attached. Do it regularly and you'll appreciate the added convience.
As well, some 2nd generation OBW's had a tri coat paint which was pearlized. Painting any fender bender issues was more costly and required a painter who knew what he was doing to get a good match.
Other than those issues, both generations were pretty bullet proof, which is why I went on to buy another one in 2012. Good Luck in your search!