I'd think the data logging files would be quite small so a cheap 2 GB microSD card would be plenty good enough.
Smaller capacity cards of less than 2 GB are getting more and more difficult to find.
I still have a couple of "antique" 128 MB cards that work well enough to move files to the 3D printer - but size there seems to not be much of an issue.
The cards are also sold by "class" which means transfer speed.
On the Raspberry Pi, class 10 is necessary because the operating system runs from the card.
But for Arduino data logging a cheaper class 4 would be fine.
You can test your cards with free programs to verify both speed and capacity. I find
SD Card SpeedOut 0.5 to be more than adequate.
My collection of cards are organized into individual tiny zip-lock bags. Each bag contains a card and a short description of the contents of the card's data.
RGB eParrot Questions and Answers SD card collection.png (175.56 kB. 350x466 - viewed 1905 times.)