I was told that SFX is much better than RCI in terms of availability.
This is not true. SFX has fairly good availability in Mexico but rather poor availability in the U.S. You also cannot search the inventory they have so will be unable to verify whether they have what you want when you are deciding where to deposit your week for an exchange. You can get SFX membership without buying from Vidanta and see for yourself.
+ 150,000 points holiday inn club vacation(hicv) valued at $38,000.
The "trade in your old timeshare" gambit is a frequent selling point/scam with Mexican timeshares. They don't want your timeshare and will not take it off your hands. Instead, they will provide your information to a third party timeshare disposal company that will try to charge you a fee and merely advertise the timeshare for sale or try to give it away on Timeshare Nation. They will never have you transfer the timeshare to them because they don't want it. If you think back to the sales presentation, they never requested any proof of ownership from you for that timeshare, did they? What for profit organization can you think of that would give you $38,000 in credit for something that you only told you that you own but didn't prove you own? If you search through this forum you will find many threads with people documenting their transactions with Vidanta in which they still have their old timeshare (I'm one). It is amusing when as part of the transaction the third party company tries to sell you the old timeshare that they were supposed to move to someone else.
They are saying that vidanta is better quality than HICV points system and they are suppose to expand as they build the kingdom of son resorts and theme parks.
They are building new resorts, but at a much higher level than the entry level you would be buying in at. They are also building them rather slowly - their resort in East Cape near Los Cabos was supposed to open years ago but they have barely started it. The theme park in Nuevo Vallarta was supposed to open in 2018. They do have very nice resorts, but the Vidanta way is to get you on a never ending upgrade process in order to access the higher levels - if you purchase with them they will prevent you from exchanging into any level of the resort above what you own. If you don't own with them, you can exchange into whatever level your exchange system is affiliated, though they may limit it to 1 in 3 years, etc. Bottom line is that it is way less expensive to exchange into a Vidanta resort than it is to reserve as an owner even after you have paid to be an owner.