Personally for going a fair bit further then what OEM did, ie a bigger turbo+extra fuel, I always think standalone is the way to go. Though can be pricey, and leave you with law issues regarding tuning/emmissions etc.
Im not sure how worse it is, dont think you will get a definate answer as it will depend on your setup, but a standalone will get better fuel economy then a woos chip. Min $1000 more cost though
. It depends on how far you want to go.