Well I would look at both and see. With the car securely jacked up,disconnect the spring bolt, remove the 1/2 shaft. Mark your camber position first so you don't loose your alignement,then crank it out so you can remove the shaft. Keep the shaft level. I like to move the caliper up off the rotor. Now like this you have isolated the bearings, the only thing moving are the bearings. If the rotate smooth without endplay or a lot of runout then they're probably ok. If you feel binding,roughness, etc then you should replace the bearings and if you do use quality parts,no cheap kits,imported parts etc.
U-joints should be tight, look for play and rust dust at the caps. Maybe even a cracked joint.
I addressed a similar question on the diff binding as well. Most common would be backed out RG bolts that shear off.
