If you are only going to run 33's I'd just stick with the D30. But if you think you might go bigger down the road and will be upgrading axles, then I'd grab them and then take all the time you need to build them up. Wheel on the 33's until you get them built and ready to put in. The only problem with the waggy axles is that the rear is narrower than the one in your XJ. The front is about 61.5" WMS-WMS and the rear is 58" WMS-WMS. So you would need to run spacers. The front is nice because it's not much wider than the D30 and you get real hubs, bigger shafts and U-Joints, ring and pinion and can go high steer. Probably the biggest advantage would be the high steer. But people will argue that the D44 isn't that much better than a HP D30. It's all opinion. I would have just gotten a HP D30 if the rear I got wasn't 6 lug. So I built a D44 to match the rear. Let me know if you have any questions. Also, 53guy on here did an awesome write up on putting a Waggy 44 up front and a Isuzu 44 in the rear. Definitely check that out if you go the D44 route.
-Matt