Welcome to our forum.
Also the lifetime shell is nice.
To start with the Envoy and Dove canyon are 2 pretty different spas. one has 2 pumps the other has 5 one per seat plus mega more jets not that its that big of a deal, maybe it is for you? . And as noted a bit of a price difference. Both are good quality. Have you wet tested yet? Don't worry about the shell warranty most spa's of quality are probably not going to have an issue. Equipment wise both are 5 years. How are the dealers? Filtration wise 3 vs 5 which would you rather clean, 5 or 3 both systems will keep your spa clean with the same amount of chems either way. You would be happy with either but I would wet test and pic what you like best. Have you checked out other brands, Jacuzzi,Sundance Arctic,Marquis? Plenty of others out their to look at, but maybe not where you live? Many people get caught up in the hype of how many filters how many jets so on and so on. Wet test, and find what works best for your needs.