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The main differences between the 2 spas are as follows:
Envoy has a lounge, Vanguard has a cool down seat
Envoy has a very nice water feature, Vanguard has a very simple one
Envoy has wrist jets, Vanguard does not
Envoy comes standard with Tri-X filters, Vanguard can be upgraded to Tri-X filters with minimal investment
Envoy has a MotoMassage DX, Vanguard has a MotoMassage DX and standard MotoMassage
Operating costs are virtually identical
I hope this helps. I love the Envoy, but the Vanguard is very nice, too. You can't go wrong with either.
Terminator