Grandee has a few thing the Siberian doesn't have. Figure out if these are imortant to you, and then go with the one you like. Wet test. But hurry....
Here are some of the things a Grandee has that you will not find on the Siberian:
Moto Massage (two of those babies, in fact).
Soothing Seven jets.
Titanium heater (Sib is Stainless Steel, but has the same warranty)
No-bypass filtration.
Can use the Tri-X filters (extra cost).
Color-chagning light (standard on White & Pearl).
Water feature that runs off the circ pump (so it can run with jets off).
Three colors of siding available.
Shell colors: Pearl, White, Jade and Blue. These colors are changing, so supply may be limited. Your dealer may have some of these in stock.
Main control panel on side of tub and Aux panel inside.
Grandee is 8'4 x 7'7" and 38" tall. Siberian is 7'7" square and 38" tall.
Grandee has a 6KW heater, Siberian a 4KW (this doesn't make any difference that you would notice, even in the cold).
Grandee has smaller pumps than Siberian, but the jet action is the same - you can't run as many jets at the same time.
Features the Siberian has that the Grandee doesn't have:
Flat water feature -
Two-speed pump on jet 'A' (only, not jet 'B' - this is so you can run the water feature with the jets on low. Kinda cool if you like mellow water circulation now and then also).
Lower price.
Foot massage dome.
One seat with 6 large jets (put spinners in all 6 jets and you have one of my favorite seats next to a Moto)
One seat with 18 jets - one of which is a 'Jetstream Jet,' which is like a firehose under water.