Let me start by saying both are very nice spa's, and you would be happy with either!!
Looking at the specs sheet feature for feature there are differences.
Vangaurd 7"3 X 7'3 X 36" J-365 7'6 X 7' X 38"
32 jets 32 jets
circ pump yes circ pump yes
water features squirting water water fall with colored lights looks nice
2, 1.65 continuous pumps 2, 2.5 continuous pumps 1 is a 2 speed for more variation
150 sq ft filtration (no by-pass) 120 sq filtration with debris trap (no one has one) only 1 pmp is by pass 1
is dedicated to the circ pmp both do a
great job it really comes down to how well you maintain your chemicals.
colored lights yes yes lighted water fall and low beverage light indicators
Shell color option HS 4 Jacuzzi 9
stereo yes yes
controls reach over side (one remote on top) mounted on top for easy access
ABS pan (base) no yes 6" no wood rot or infestation
Foot jets, 2 not well placed (IMO)4 calf Foot jets yes 5 with 4 calf jets
Warranty 7 years shell/surface Jacuzzi 10 year
plumbing 5 5
component 5 5
stereo 1 2
heater 5 year no fault 5 year its never your fault least in the 6 yrs we have been doing it, its
always electrical if anything not chemical or other.
I don't know, each one is very nice spa in its own way, prices will vary. In this area J-365 8495.00 Vangaurd prolly around 9000+
Like everyone said wet test and let your body decide, but when you look at the features the J-365 has to offer, its hard to beat.
Insulation wise and power consumption should be pretty close to the same doubt any consumer could tell the difference in real world everyday use.
Overall let your body decide which you like better, and which one fits your needs comfort wise and how many people you can fit in it, if that matters also as mentioned, make sure the dealer is good, get references if any doubt.
See that wasn't so bad yet!!
No need for popcorn yet.
Lets keep the replies civil, I will!