The reason I think that it is more versatile is the fact that it can hold its heat much better and can be passed around to more people. It can be used by yourself or with other people. The PD is pretty much a solo piece, as heat retention (or, more precisely, the amount of time it takes to heat back up to its ideal temperature) is rather (s)low. It is recommended to be used as a solo piece, rather than used with 5 people who vape out of it continually.
Also, Da Buddha's whip can be easily attached to any glass like a bubbler or a bong very easily (even if it does not have a GONG connection). The PD stem can only be used on 14mm GONG bowls (however, you can always attach a whip to the PD stem, but then why not just stick with the Da Buddha?).
If efficiency is your concern, you can pack smaller bowls. Because of the size of the wand, most people pack large bowls which lead to a larger concentration of vapor on the exhale (which is wasted vapor). Although because of the whip tube (the longer distance the vapor has to travel away from the heat source), more vapor condensation is inevitable compared to the PD. However, you can collect this vapor to make oil and in this regard, the efficiency leverage that the PD has is a moot argument.
If you want me to give my opinion on whether you should get a Purple Days Pandora or a MyrtleZap, I'll gladly try to steer you towards a MZ.