Are there advantages to a retofit kit?
the retrokit gives maximum flexability because its a custom build by you or someone else. Usually covering the entire tank. This also ends up giving you more room for the bulbs to be spaced or for things to be added/changed at a later date. A prebuilt hood is basicly how it is when it was built and if you want to change things then your better off buying a new one.
If your deadly afriad of doing your own wiring then a retrokit might not be for you but honestly the wiring is not that hard and most kits come with great instructions.