For this thing I first downloaded CloudOn to give it a test drive. I don't typically find myself creating or editing documents on the go, so I'll be evaluating these primarily on interface, intuitiveness and usability rather than practical application. CloudOn was easy to link to Google Drive. I edited an existing document and also created a new one. The one huge, glaringly obvious deficiency in CloudOn is lack of auto-correction, which I automatically come to expect in everything I do nowadays.
I next tried Quickoffice, which I immediately noticed DOES automatic auto-correction. Yay! Perhaps this shouldn't be the deal-breaker when the app can do so much more, but when you expect it to be there and it isn't, it's kind of a drag. So Quickoffice wins this battle of the document apps. I could see myself using this if I had reason to be working on office documents on the go.
I opted not to download and try out SignNow since I have nothing that needs signing, but it's nice to know it's around.