Over the years I've used the slowest cards and class 10 and better. What article did you read to have you ask this question?
I tend to buy the better cards today since it's cheap as borsch (comparing cheapest to say the Samsung EVO class cards.)
As to roots, I like the XDA Forums for ROMS and tutorials.
I'm pretty sure I'm going to root my on5 but I'm wondering what size as card and speed of the card should I use plus anyone who has valuable information or tips for rooting my galaxy on5 or maybe a link to instructions to root my phone