I always prefer to work with people that are good in CHANGING existing code as it REALLY requires them to understand (other's) code...

there are just too many "from-scratch-coders" out there that are feeling more like "coding artists" and create crap code that does not obey any standards or not to think-of even design patterns...

Those that use available libraries are usually the much more experienced ones..

Brings up a good interview-question: your 3 favourite libs - and why?

so the best team staffing would be to get "Changing Code People" and build your project from scratch (but still based on good basic libs of course) ...