So, I can't really compare apples to apples with RCI and Interval. My RCI account is via my HGV membership, so I don't have Platinum benefits or whatever. My Interval account is using a (now very high) Bluegreen 2 BR as an exchange, so YMWV (will vary, LOL).
I'm searching for Nuevo Vallarta, as it looks like RM no longer has anything other than The Bliss and Lower via RCI (No Grand Bliss, and No Grand Luxxe).
RCI - Things to remember:
1) NO GUEST CERTS
2) 1-4 rule
2 BR Grand Luxxe @ Vidanta NV = 4,800 HGV points, plus $249 Exchange fee. My MF are about $0.18/point, so that would have me at:
$1,113 plus the Vidanta imposed resort fees of: $950
Total: $2,063
Interval: No restriction on Guest certs, AFAIK. No 1-whatever rule (as of yet)
My Exchange (2 BR) costs me now $1,200 in MF plus the $219 Exchange fee = $1,439
Plus the Vidanta-imposed resort fee of: $950
Total: $2,389
SFX:
I'm Diamond, so I get "free upgrade" to next larger unit. I deposit a 1 BR week from HGV, so my MF and HGV fees are:
$562
Plus the SFX $149 Exchange fee, plus the $299 GL Upgrade fee = $1,010
Plus the now Vidanta imposed $900 resort fee = $1,910
Now, I don't know about RCI, but with Interval, you'll get an email from Vidanta (looks like it comes from Interval, but it doesn't) about 30 days prior to check-in telling you that your stay will be cancelled if you don't pre-pay the resort fee in 2 weeks. When you call the phone # to pre-pay, you get Vidanta (not Interval) and they typically offer you a 50% credit towards F&B. So $950 = $475 in F&B credit (ie, you eat/drink $500 worth of stuff, and it gets offset by $425 since you paid $950 in Resort Fees).