My FT came to play in 2007 and I still have it. Flintstones arrived in 2012, when I found a great example for just $1,600.

Adults love Fish Tales and over time I've had 5 offers to buy it at bought price+ and said no to all.
I enjoy the video mode, especially shooting the jet skiers, also some other fun modes.
Adults enjoy the Flintstones art and sound package, kids glom all over it. I like the fact Williams outfitted it with DCS Stereo Sound, one of the few titles they did that too. Turn it up and hear the difference.

They are different when you spend time with each of them - heck, you only live once.
Find the money, get a loan - get both. I believe you won't have trouble later selling what you like the least. Each are popular to pinheads and non-pinheads alike.
IF I HAD to pick JUST one, I'd go with FT - the ipdb.org ranking for this has been consistent since 2008, Top 25 every year.