I can't speak for Cypress Harbour Platinum, but we own a 2bdrm Gold lockoff at Grande Vista. We've always reserved the best demand week we can which in our case is Memorial Day week although there are some higher demand weeks later in the year too.
With Platinum season at Cypress Harbour, you will have more high demand weeks to choose from for making your reservation than you will with Grande Vista.
That being said, MGV is rated slightly higher than Cypress Harbour by II, plus you have the lockoff feature.
We have traded our 2bdrm Gold for Platinum the past 4 years; once back into MGV, twice into Hilton Head and once into Las Vegas. We did not use the lockoff feature on these trades as we felt we needed the 2bdrm strength to get the trades we wanted...and we did.
The trading power between the two is probably similar. If you feel you will use the lockoff feature go with MGV, if you are not sure then Cypress may be more for you.