Many choose Scrum (ScrumProcess) because it's easy to implement and many find that Scrum doesn't address all the issues involved in the life-cycle of a software system.
In my experience you need to consider at least the list of XP practises: http://www.extremeprogramming.org/rules.html in addition to Scrum.
You should also consider some of the extensions of XP, i.e. DeveloperStories, FrequentReleases (one week not four!), PairProgramming, and TestDrivenDevelopment.