There is actually no "better" in terms of strollers, at least not in the general meaning of the word. Always, "better" depends on many many factors, from the budget, baby's age, parent's need, use of the stroller, most occuring terrain and so on. For example, if you have a 3 month old baby, the Butterfly or the Aer, even if, by quality, superior will not be the right = "better" choice. On the other hand, if your budget is 200, you will simply not be able to afford one of those two, so again, they wouldn't be the better choice.
If, however, I will take away these priorities and needs, quality-wise, the Butterfly and the Aer would be my favourites. What is better about them is not just the quality of materials and wheel suspension, but also the much roomier seat with a tall seat back, and also the more upright seat than the other two which are actually rather slanted. Many parents and kids don't like to be in this half-sitting position where kids often slide down a bit, being held by the harness straps more than sitting.
I would most probably choose the Bugaboo Butterfly because of the leg rest and bumper bar already included.