The problem with the D30 and 35's is really gearing. 4.88's are OK if you're not doing much highway driving or there are no big hills. Offroad, you won't notice it much since you're geared fairly low anyway, BUT those times when you need to be doing 70mph to stay with traffic, can be tough. Regearing the axles lower helps two fold. First it helps offroad by giving you a lower overall gear ratio. Secondly it helps you onroad with overall gearing. The problem with swapping in a transmission with lower gears is that you end up with larger gaps between the gears. Not to mention to get those lower gears you're either giving up 5th or adding another 100lbs with wider gear splits. Getting lower gears in the transfer case only help with offroad. Although if you're mainly looking at offroad, doing the transfer case gears will give you more bang for the buck.
So if you're using your Jeep as a daily driver, it's probably best to upgrade the axles so you can go with the proper ratio.
Strength wise, if I was going with a D44, I'd get a real D44. Then you'd get the advantage of larger stub axles, manual hubs, larger knuckles, Hi-Steering, etc. It would also help set you up for going larger or even an engine swap. If you go with ultra low gears you'll want all the strength you can get since torque is also multiplied. Another thing to consider is that if you get hardened shafts and upgrade from the 297x to the 760x, you'll be moving the weak point else where.
Also, keep in mind the choice all depends on how big you want to go, how you dive and where you go. Rockcrawling requires more strength then sand or mud. Out west it's all about super low gears but move to the Midwest or PNW and you've got to give it some throttle as well.
There are a lot of choices to make and I've never heard anyone regret upgrading.