So, I now have both an original PD from and the Better Days.
So far, they operate almost identically, though there are one or two differences.
The BD (like I'm told some others like Woodeez) has an additional screen the PD does not have (at least visible) - the BD has a screen directly under the bar where you insert the tube. The PD doesn't have one right there, at least that I can see. However, I've had no problem with the PD from the lack of a screen there.
The PD's internal hardware is more tightly fitted into the unit - doesn't feel like anything moves around in there. The Better Days seems a bit looser - when you shake the unit a little, you can feel some motion inside. Not a lot, but some. Hasn't affected any use yet.
Final functional difference, though this may be just the two units I have - my Better Days seems to get a little hotter than my Purple Days. Again, this may just be slight variance from unit to unit, or may be due to an actual difference in settings.
Overall, they both work awesome. I love both of them, and use them both. As I'm trying to quit smoking tobacco (trying to vape) I now use one of them for the tobacco, the other one for my other herbs.
Aesthetics - The Purple Days has a nicer looking piece of leather for the bottom, the wood is a little prettier, and came with more accessories - 3 tubes, the aroma cup, cleaning bottle, etc. The Better Days comes with two tubes, the power supply and the vape itself.
I'd gladly recommend either unit. I have not had a chance to compare either to a Woodeez or the now (officially?) RoHS compliant Aromazap. I did have a vape session using my BD with a friend who owns a PD, and though he was surprised, he didn't notice any difference either.
For me, the advantage to the BD was that I ordered it and it came almost immediately. However, my PD took only a week longer to come. I was lucky re the PD list - Vapenow told me I was one of the last people they allowed to get added to the list, instead of having to wait for more to come in before ordering.
If you do get stuck waiting on a PD (though rumor has it that will not be a problem in the near future) and you need an excellent vape for medical reasons, making waiting much harder, the BD is a fine substitute. I assume Aromazap/Myrtlezap would also be a substitute, though I haven't used one. At the time I ordered the BD, I hadn't heard about some of the changes AZ/MZ made.
That being said, I'd advise the Better Days to set up a website for his product (I think he is planning to), on which he should fully disclose all of the materials he uses and any other info, like what improvements he feels he has made. And as someone who works in the law, I would advise a DIFFERENT NAME. You don't need a potentially trademark-infringing name to make your product appear when a person searches for one like it. Google searches do that by default for most types of things - search for a vapezilla, you'll get hits for that and for almost every vape of a similar design, from knock-offs to improvements.
ANyway, both my BD and PD are so good, they are now the only vapes I'm using. No longer using my Herbalaire, vapezilla original, natural goods digital, Vapor Brothers or Vapolution.
I do wish the wonderful Vapolution AIW bowl would fit my PD or BD- its just a little bit too wide to use with them. Maybe one of these guys will make a similar stem for a log-style vape? Espec. if it stays hard to get the RevolVere PD stems.