Interesting choice by Burger King, I haven't heard of them doing a wagyu burger in the US. I guess not a big surprise that it's disappointing from Burger King.
I'd say the wagyu hamburger meet is only slighty better than the other one that I buy. It's a little fattier and juicier than the other.
This is the other one I use, it's about $7.99 compared to the wagyu at $10.99. Worth a try though, you'll probably like it!