which card for a XZ-2 ?
I bought this one for 35$, and it seems to work fine.
The Extreme products are one step down from the fastest Sandisk makes (Extreme Pro). Even if you're not buying Sandisk, it can be helpful to look at their product line for cameras. (Hint: check the box under the level of card to see all the products for that level).
It would be easier to choose a card if Olympus put the maximum transfer rate that the camera can actually DO into their specifications. I don't see it there.