Nokia Sports Tracker is great because it has a facility to easily upload to your routes/workouts to your onlibe account on Nokia’s server. You can log on and recall these, download to the phone etc at will.
Viewranger is not an application that allows routes to be saved or analysed by a web server application. Route planning can only be done on the phone itself, but it’s a good app. that gives good detail. With Viewranger map chooser you can get up and running with a tailored map form £20. Bargain!
I think you should go for both applications, but I would hesitate to say which is best. That’s somewhat subjective.