Hi,
First of all and as you already know I think, logvapes are known to be really (if not the most) efficient!
It is made for using as tiny load as possible for the best extraction. I own a Wychwood (no longer produced) and I'm in the waiting list for a Hi, actually my turn has come but I'm in waiting for money :/ I bought the WW cause I really needed a logvape after I've read all good things about them : no whip, perfect to use with glass, discrete, pretty, economic (designed to be plugged 24/24 7/7) = so you don't wait for preheat, versatile : you can choose a lot of different kinds of stem to modify your experience, etc etc... AND simplicity : which for me enhance the vaporizing experience compare to have to deal with bags, whips, batteries...
So why did I choosed the Hi over any other? I won't talk much for the PD as I don't own one..
1) The Hi run hotter than PD at 12v but you can still buy some VVPS or other VV accessories (check on the forum) to get more voltage control. In the other hand you can always get a lower temp by having more distance between load and heater.
2) The Hi is more durable and user replaceable (heaters, etc..)
3) The Hi is a one-man made craftsmanship which evolute with the time : just read the thread !
Now you can choose a Stainless Steel heater cover or a glass one or an Hibrid one (glass and SS sleeve) + any wood you would like to.
4) The Hi is the most tiny and small and of course you can still ask for a custom made but I'm pretty sure Alan (Heat Island creator) is making the most tiny and finest log actually existing.
There is probably much more things to tell but some else will have pleasure to answer you, I'm sure.. Also I don't own my Hi yet so I can't talk to much, hehe