As far as I'm aware, rating the dependability of solid state media is kind of complex.
On one hand, the larger any flash media is, the longer it's service life, since each cell takes longer to get written to each time you fill up the card. If we assume a memory cell can be written to 1000 times before it fails, then a card with double the cells is twice as durable. On the other hand, with twice as many cells, you also have twice the chance of some of those cells failing. Not to mention the card stays the same size, so all those cells are getting crammed in there and it may count for something too.
To put it simply, a 64GB card will last longer than a 32GB card, but may have an increased chance of data corruption. Long-term total failure vs. short term local failure in other words.
I'm just theorizing here though, I have two 64GB cards by Lexar and Sandisk and both work fine after months of use, no problems at all.