My ..02
First I'm an older guy, sooo...
I'll disagree on the 97-98 theme, respectively I must add.
The 96 is my choice, I'll explain below.
I have owned a few xj's in my lifetime.
87'2dr auto,offrd pkg D44.4L
91'4dr 5spd, sprt 4L
90'4dr auto ltd 4L
now a 96' 2dr 5spd, SE, 4L
I really liked my 87, but it got totalled.
Realistically, the 96' has the upgraded front axle and all of the "newer year" important "wheelable Upgrades" that I was looking for.
And yes the 96' engine has the lower RPM torque increase as well. In thanks partly due to OBD II, which the 96' also has. I really looked at what was best personnally for the upgrades I wanted.
Now the newer ones do have a passenger side airbag and the 96' only has the drivers side. The 96 is "suppose" to be more tolerable to smaller lifts and viberation problems encountered with the newer xj's from posts I've read too.
And parts for the older models is way more easier to find, and priced lower generally, and in the boneyard as well. So you might add the 96' too.