Upload & Sell: On
I have not used Photomatx but use Nik all the time.
Before Nik was bought by Google, I had most of their "collection" already. But I did start out very early with just Viveza and Dfine.
I am VERY satisfied with their entire collection. And what plug ins I didn't have prior to Google buying them out, I got free when Google did. So that was a plus.
Try both and choose.
In my readings, both are very fine plug ins.