I have both and love both. I will go as far as saying that I just might prefer the Plume Veil.
The Plume Veil is the most open RDA I have ever tried, the three adjustable air flow systems can really get an incredible amount of air moving through it. The flavor is incredible and if you sub-ohm vape, the vapor production is weather changing. I get claustrophobic when there isn't enough air flow, and this doesn't give me that problem at all.
As for the Stillare, it is definitely the sturdiest and most solid RDA I have. It just feels of quality when you hold it. The flavor isn't quite as great as the Plume, but it's still great. It's vapor production is 'very nice, I like a lot' too.
Personally, I feel that the Plume Veil actually has a deeper
juice well than the Stillare, but not by much. The Plume Veil v1.5 is going to come with a deeper
juice well, one of the new additions.
Good luck with your decision and enjoy your new RDA!