They are basically the same, but not exactly.
"Worth it" means "at least equal to the investment (time, money, effort, etc.) that went into producing the result.
This wine cost $250, but it is worth it.
"Worthwhile" means "producing a positive result".
Charity work is a worthwhile hobby. Watching television, not so much.
I would say that "worthwhile" is inherent in the thing, while "worth it" depends on what was paid/expended for it.
In your example, I would use "worth it", and not "worthwhile".
Bruce