I think it is two fold. Westin Flex is new and perhaps the demographic that Sheraton Flex targets vs Westin Flex. Vistana has two huge sales centers in Orlando selling Sheraton Flex. Likely mostly selling to young families and probably people that shouldn't be buying the product. Westin Flex is targeting a higher income level demographic and they likely aren't as eager to get out from under MFs as those buying Sheraton Flex.
I think you’re right. The minimum buy-in for SFlex is lower than WFlex and the purchase price per SO is also less. I’m surprised at how many small (And really unusable) SFlex packages have come to the market.
WFlex buyers are likely more financially established. I have seen a few WFlex on RedWeek - and they seem to have gone at prices that were higher than I was expecting.
Westin Flex has quite a few Maui resorts and I can also see it appealing to folks who want the flexibility (and do not necessarily want to bother with StarOption trading)
There is a lot of Nanea in WFlex as well as the other Maui resorts and WPORV. These seem to be the resorts that most people want to use SO to trade into.
WFlex even on resale gives you access to these resorts at the 12 month mark. In this sense, a resale WFlex package is better than buying a mandatory WKV or SVV week to use for SO trading into Maui. Yes, the MF/SO isn’t as good compared to the mainland resorts, but it’s not bad compared to some of the island properties.
If you want to go spend a week in Maui during peak season, you're still better off with actually owning one of those weeks.
If you want to add a few days to a Maui stay or want a bit more flexibility on check-in day, without playing the SO lotto, then a resale WFlex may be part of a healthy TS portfolio.