should you caster be the same on both wheels?

so i have had 4 alignments and i am being told that my caster should be about a 1/2 a degree different with the right side higher then the left. this last time they got it to 2 on the left and 2.7 on the right. they say it is for the crown on the road so it tracks good but i still do not know. i see people on here say 2.4 to 3.0 is perfect but is that both sides or just one.
i know you want the camber the same on both.

so should they be the same or different?

 

i dunno, when i got in my accident i was going back and forth with the body shop cause i was having tire rubbing issues on the wreck side, so they checked the alignment and the guy also explained to me that its normal to set it different, due to the curvature of the roads...makes sense to me i guess, but on flat roads (or seemingly flat roads) my truck still rides straight....