I haven't explored either of those, but I've used DocScan HD and I'm pretty pleased with it. I don't have a large volume of iOS scanning to do, so it works fine for me.
I have used both of them and they both are working well. However, Scaner pro looks better to me. It has an additional advantage that it supports many languages including English, French, German, Italian, Japanese, Portuguese, Russian, Simplified Chinese, Spanish and Turkish. While, TurboScan supports only English & Russian.
On the other hand, Genius Scan+ and Doc Scan Pro are also great in terms of usage