they are good if you dont have much money or fans. Or if you dont want to wait 16 days or so before you want to upgrade something else.

It is a gradual upgrade, it all costs the same and takes the same time in the end, so it doesnt matter which you do, it is only that if you upgrade the whole thing it will take a lot of time and you cant take advantage of the increase in fans. If you do the gradual upgrade, your attendance can increase gradually and you wont be left with so many empty seats.