What spindle diameter should cranks have?

 I know that most people want the largest diameter, which would be 30mm, however the new DUB system from Sram (29mm) has me hooked: It allows the use of ANY current BB type. At first I'm like "Ugh!, another standard", but after installing two of the new DUB set-ups, I am sold. Press fit should cease to exist in my book (constant issues including creaking) and have only some type of threaded BB cups, such as the current threaded GPX style.