If you're just going to be doing PPG, then high hang points are fine and your flight will feel more stable, but you do get a little less feel for what the wing is up to. If you're converting from paragliding, and are used to 'active flying', then low hang points are for you - the wing will feel more responsive but as has already been mentioned, the flight can get a little bumpy. You could always go for for a happy medium and opt' for semi high hang points.pereonally, I find launching with lower hang points easier but I suppose its just what you're used too.
Hope that helps