External Storage Options for MBP non-retina
Replacing your optical drive would seem a logic choice to me. No wires, fast transfer speeds and you have your disk always with you. If storage is your main concert, just go for an HD (And replace your SSD with a bigger one while you are at it...)

It is not expensive at all. You need a philips screwdriver, a hard drive enclosure kit specially made to fit the Unibody MacBook Pro, and a new hard drive. This enclosure holds the drive that fits into the MacBook Pro’s optical drive slot and costs about $40. 

Buy it here: iFixit, MaxUpgrades, MacSales or OptiBay