there is no advantage or disadvantages between these 2.
Now all BCDs are moving to integrated weight.
Some like it integrated , some like it conventional. It depend on the user itself.
Normally using weights around the waist can make you feel uncomfortable on the waist bone, especially
to skinny people.
some may advise standard protocol is using the weight around the waist. If anything happen underwater ,if they need to release the weight they know where to look for.
Somehow i dont think this advise you should worry about.
Most integrated BCD are now design to perfect trimming underwater.