The plane that YOU build will have better glue joints because you will take your time and use a better quality glue. Tools you purchase will be used on future kits. A bottle of wood glue should do several planes (depending on size of plane and glue bottle). Pride of workmanship will last forever. Many parts will be transferable to next plane when this one dies. I prefer to build my own.

There is nothing wrong with buying a ARF/RTF to become a pilot. But you need to build a kit to become a "modeler" IMO.