Flash memory chips can be SLC or MLC. I believe the top cards use SLC chips while "cheaper" cards use MLC memory chips.
SLC -
single-level cell
MLC -
multi-level cell
https://en.wikipedia.org/wiki/Flash_memory
https://en.wikipedia.org/wiki/Multi-level_cell
Probably more than you would like to know:
https://en.wikipedia.org/wiki/Flash_memory#NAND_flash
In short, SLC memory cards have similar read/write speeds (Sandisk Ultra, Extreme, ...) while MLC cards have a much hirger READ speed.
Delkin seems to have a SLC card (CombatFlash).
I also just bought a Delkin 700x 32GB and it performs well (Canon 7D). It's a good performance/price ratio. My other cards nowadays are Transcend 400x and 600x which have a good price/quality/performance. I find them similar to Delkin's. Delkin a little faster while downloading.
My 0.02.