A bit of both..... I use sight to get the picture where I want it, then measure to make sure it is exactly right.
Yin and yang - balance - everything in moderation..... not just for life but hanging pictures too!
A bit of both. My late husband who had been an engineer always did everything precisely and would take forever to hang anything on the wall. The tape measure, spirit level and bits and bobs came out before he was happy. It used to drive me nuts!