It very much depends on the image to get the best out of these apps I think, Prisma has LOTS of choices but you get one click and no other way to edit them. It also puts the logo on each image which is a bit intrusive – maybe you can pay to get rid of it?
Here is the same image of Taz, my seal point Birman boy sniffing wisteria on my fence – this time done in Waterlogue. I really like the very watercolour like finish you get in this app. Its frustrating because the limit of the image file is such you cannot output really big files for print 😦
Here are a couple of slideshows showing off different effects for Prisma – one for a portrait shot of Cognac and one for Taz.
I am surprised at the variety and at the detail and effectiveness of these apps – do you have any favourite apps you use for working with images?