Maybe I'm biased because I have a pair, but Thai Silk flowerhorns are my fave. The next in line for me would be the golden monkey flowerhorn. In 2009, a golden monkey sold for 600,000 dollars in a Malaysian exhibit.
Any quality Flowerhorn could make a worthy show piece. Everyone has different opinions on what they think makes a good show piece so you won't get the same answer. I personally love true Classic Kamfa and pearless Red Dragons.