Welcome to our forum.
Unfortunately, none of my local dealers for either brand have filled models available to wet test.
As of today they don't. Walk into the HS dealer with a Jacuzzi flyer in hand and tell them to give you a call when they have a Grandee filled and then do the opposite with the Jacuzzi dealer. Many dealers rotate which tubs they fill and you might influence their next choice and timing. At no time has the buyer had more leverage IMO. Now I don't mean to imply that you should jerk them around, but they should be able to spot serious buyers and accomodate them.
I think part of the problem right now is many dealers' inventory is low. Some may choose to carry say a Vanguard on their floor, but not a Grandee since they are so similar.I agree though, you should get your dealers to fill the tub you want so you can test them out.
I am curious spec wise what makes the Grandee or other spas in the HS line better, sorry better is a bad word (not similar) than the 300 series specially some of the smaller sized ones? The Jacuzzi has 2-2.5 hp pumps with a 24hr 220v circ vs the 2 2.5 hp pumps and the (110v circ pump?) of the Grandee with 39 jets. The J-365 has 32 jets the J-375 has 36 plus 12 leg jets. same pumps plus circ. same with the J-335 J-345 and the J-355. Add waterfall colored lights and ABS pan. Other than filtration, I dont see a lot there, not to compare it to the HS line. I would agree the 300 lines up with tiger river but its also lines up against the HS line as well. With out starting a huge debate I would love to hear some opinions as to why its a step above??