I never quite get the "Roll20" is simpler comment as both have nearly identical UIs. From a GM perspective there is the initial purchase and setup for Foundry which is more complex, but from a player perspective they are mostly the same with each having some areas they are better at in a small way. Some of that depends on the game system you're playing and how it was implemented in both.
@Geoff R Evil Regarding the dice in Foundry, the "Dice Tray" and "Dice so Nice" modules are a must for every game. Both are well supported. As for the scrolling, doesn't that affect Roll20 as well?