I've just stayed at the Andaz but walked through the Grand Wailea and heard things about it on our trip. Two big takeaways i had... Grand Wailea is much much bigger. At some point someone (uber driver?) made a comment that the Grand Wailea would have 1000 kids on the property over the Christmas break. Also, the Andaz is the only newly built property on the island so much more modern. From afar the Grand Wailea definitely looks OLD. have no idea what the rooms are like though and when they've seen a refurb.

Only you can decide whether $200 is worth the upgrade...but I definitely saw the Andaz as an upgrade vs. the Grand Wailea.