Dunno which U-joints you've been working on, but the ones I'm dealing
with don't have room to get a pair of slip joint pliers into position -
no pliers I've got that can open wide enough to go around the cups are
skinny enough to get in there and do the job. The clips I'm working with
live on the inside of the ears of the driveshaft, clipped into a groove
on the outside diameter of the cups so as to perform as stops,
preventing the otherwise free-floating cups from moving outward through
the ears.

As far as snap ring pliers, there's nothing to get a "bite" on - These
are "hole-free", external snap-rings - The ends have to move away from
each other to expand them enough to remove from the groove they're
seated in on the cups. The "crossed screwdrivers" I mentioned are the
only way that seems to be possible, and they have to be pretty skinny
screwdrivers to fit into the small gap that's available to work in. Even
then, it's a severe pain in the backside to get the job done.

It's the "tear it apart" stage that's turning out to be the killer,
requiring anywhere from five minutes to half an hour (or more!) of
dinking around trying to get each of the old clips off so that the cups
can be pulled. Multiply that by twelve rings (3 U-joint driveshaft), and
you're talking quite a bit of wasted time and effort fighting with the
darn things.

Putting this driveshaft back together is a cake-walk - spider into
position, cups onto ends of spider through driveshaft ears, position the
clip, and give a little push with a thumb - Done, in just a few seconds
per clip. They practically install themselves. Reassembly from "totally
disassembled" to "Ready to put back on the car" is a matter of five
minutes or less, total. Getting it torn down so that the new joints can
be installed takes well over an hour, most of it spent cussing at those
#*%@%*&! uncooperative snap rings.