If you plan to use a SD card or compact MicroSDXC adapter which sits flush to the MBP side you'll want to stick with SanDisk or Lexar as their warranty/mail-back is >7 working days. Other companies which are great is Patriot, GSkill & AData but warranty replacement is uber snail-mail(14+ turn-around) but the multi-pack deals from NewEgg offsets that downside. I wouldn't touch PNY SDHC cards of any type if raw speed is important, I've had class 4 cards being faster than their class 10 and some subpar class 10 cards too.
As with any storage media you'll still want to maintain a backup, I've had a few 8-32GB SD/SDHC cards fail. Oddly dirt cheap cards(Class 4) rarely fail from overheating, then again I only use SD cards on a Chromebook to transfer cloud/off-line Ubuntu work to my MBP so moving ~5GB worth of data daily is quite common.