Me personally? I'm choosing the droid because I'm struggling to see myself having fun with a lightsaber beyond the build process, but know I will enjoy the droid in the longer term.
In your situation...I might lean harder toward the lightsaber. If the experience itself is a bigger deal to you and it sounds more fun, you should do it. Beyond that, though...honestly it sounds unfair to me that he's going to have full control over his own build but then also want to have input on yours. If you both make lightsabers you can make your own independently of him and get the full experience yourself. Or you could tell him no, the droid is all you and he only gets to watch--that would only be fair if he gets to make the lightsaber without your input.
Also, if you both make lightsabers, you can have lightsaber fights. Food for thought.