I would think using the BH to dig post holes would be a snap with all the movement you have in all directions and with your tractor choices you would never have to get off the tractor to dig holes.
You might very well be right. I have a ways to go before we make the tractor purchase. Before that time, I very much want to see a hydraulic PHD in action and a TLB backhoe in action. I have not used either. I have received several recommendations from owners of both to consider the hydraulic PHD attached to the backhoe. Their experiences have been very positive so I do want to see their's in use at some point in time.