I ran 2nd and 4th generation Newfields and did a good job of shattering them...problem is, most times a junked birfield or Newfield also buggers up your inner axle splines and you are out that as well.
I now run longfields. The weak link is now the inner axle, most likely the short side since it can take less rotational twist. Since I was junking inners anyways, this becomes a cheaper replacement. I've watched Longs go thru some nasty stuff, even full throttle jumping, and the inners were what gave (both at once on one occasion).
I could always replace a birfield/inner in about 30 minutes, but 1/3 that time was cleaning all the grease and shards from inside the knuckle....now, with an inner axle, you just pull the shaft, pull the busted stub from the Longfield (or grab a spare) and slip in the new one. No more knuckle clean time, getting me back to trail riding just that much quicker.
Plus, with a clean snap of the inner axle, the inner seal should not junk out and the inside of the knuckle bell won't get more dings than it already has.
Two HARD trips out and no breakage yet, VERY impressed thus far.
Either way, you choose your weak point. Currently, my weak point is front inner axles. I carry two longs and 3 shorts, plus an old 4th gen Newfield to drop in.