SMC parts used to be illegal (for reasons that ranged from uncertain to bad). As a result, other teams tend to be a lot more familiar with the Bimba equivalents, and may be more likely to carry them as spares. But many cylinders are standard and interchangeable.
The product lines have substantial overlap, but you'll find that SMC in particular makes a lot of very heavy industrial cylinders that Bimba doesn't. But you probably don't want those anyway.
Basically, read the manuals thoroughly to familiarize yourself with what's available, and make your selection based on features, cost and availability rather than reputation. Both will likely be fine.
http://www.bimba.com/Products-and-Cad/Actuators/
http://www.smcusa.com/top-navigation...cylinders.aspx