The reason we chose for single-sided cards with a common back artprint is that:
1. We love Magic the Gathering
2. In playtests during development, most GMs said they like to "mix" different sets into a single library. This way you don't know which set you draw from when mixing.
3. Our format has 400-entries in one deck. That would be 800 when we go double-sided. This is very hard to write well.
We would not add quality, but more repetition/samey-ness in our opinion. The product may look "simple" in terms of writing, but it was actually quite challenging to make 400 great entries without getting boring.