flavor and especially aroma will be better the closer to bottling you add it. it is tough to guess the amount of fermentable sugar in fruit, so you risk over/under carbonation if you dont completely ferment it before bottling. If you keg, you can add it to the keg and adjust the force carb pressure.
best way bottling is: mash fruit into pulp(better flavor/aroma extraction, helps ferment faster, easier to sanitize, but will make beer cloudier), drop in pot of a little bit of boiling water, cover the pot and bring mix to a boil as fast as possible, put in ice bath, dump into secondary with 1-2 weeks to go, depending on strength of beer and yeast type. prime as normal