Dynamic ropes have two distinct disadvantages and two true advantages.
disadvantage 1- they stretch when weighted so when you are sitting in your saddle the rope still stretches some, when you stand up it can make it easier for the girth hitch to loose and slide down. Also when the ropes stretches, it can make advancing your prusik a little rougher. (If you have an ascender instead it won’t matter)....
Disadvantage 2- and this is a big one. Abrasion resistance. Dynamic ropes are more prone to fraying, abrasion and snags. Which when using in trees can be costly...
advantage 1 is energy absorption. Dynamic stretches which means it absorbs impact force much better than static rope. This is prevalent if you intend on doing crazy things like allowing slack in your system or falling.
advantage 2- because they are stretchy and soft, they can usually pack down smaller than a stiff static rope of the same diameter.
if anyone here has a hawk saddle ask them if they like the softer dynamic ropes (both the tether and lineman’s rope) that came with that saddle kit and you’ll quickly realize why most people use static ropes for tethers and lineman’s loops.