When we first started this business in 2007, our first game that we built was our Regular Plinko, standing at 4 feet tall. We soon realized that some clients were expecting something more grand (such as the one they had seen on the Price is Right). So we designed a larger one that stood 5.5 feet tall. But that STILL was not good enough, so we decided to go big or go home, and design an XL Plinko! This one stands 7 feet tall.
So you can to take your pick! They all work the exact same way, but it just depends on the wow affect you are going for. The most popular size is the Large, but you get what works for you and your budget.