It's hard to tell if Vikki & Vance is based on Whiskey Pete's or Primm Valley Resort & Casino or both. The Bonnie & Clyde exhibit was moved between casinos a few times. And, the wiki page for Whiskey Pete's claims that it didn't get the exhibit back until 2011; Fallout NV was released in 2010.
Considering when the game was being developed, the Bonnie and Clyde exhibit should have been at Primm Valley Resort & Casino. Flicking through the web-archive of the RoadsideAmerica article is the best evidence for this. In June 2009 and March 2010, it shows that the exhibit was at 31900 Primm Valley Blvd, which is the address of the Primm Valley Resort & Casino. Immediately after that, the archive shows that the exhibit was moved to a casino in Verdi, but it also states 'Normally at Terrible's Primm Valley Resort ... I-15 exit 1, southeastern side'. It's unclear if this specifically refers to the old name of Primm Valley Resort & Casino, or the old name of the resort as a whole (that gets confusing). But I notice 'I-15 exit 1, southeastern side'. Primm Valley Resort & Casino really is South East of this exit whereas Whisky Pete's is West of the I-15. Help me out if that's not how this works. This is the most credible thing that I could find online which pins down the Bonnie & Clyde exhibit pre-2010.
That being said, Whiskey Pete's has been associated with the Bonnie & Clyde exhibit for a very long time so it could still be the inspiration behind Vikki & Vance. I've liked looking at this forum which has a few people who were tracking the Bonnie & Clyde car years ago. There's also this blogpost. In both of those, there are claims that the Bonnie & Clyde exhibit was in Primm Valley Resort & Casino even earlier than 2009, but there's also evidence that people associated the exhibit with Whiskey Pete's during that time. Should also point out that Whiskey Pete's might always have had ownership of the exhibit.
Moving on, the location of Vikki & Vance has similarities with both casinos. It's East of the Freeway like Primm Valley, but it's opposite Bison Steve's like how Whiskey Pete's is kind of opposite Buffalo Bill's. Personally, I think the exterior of Vikki & Vance has more in common with Whiskey Pete's, but it's not a total recreation of either casino. I have no idea about the interior.
Vikki & Vance was probably a combination of both.