There can be arguments made for either using or not using. Much depends on some of the personal choices you make as you go along. Type of fish and plants is one that will change the answer. Hard alkaline fish and you may want to go with tap and choose plants to match. Set on a particular group/type of plant that requires or does far better with softer water and you may want to go ro/di. The biggest difference I see is the GH/KH of the ro versus tap. Tap may be a little too hard and require more care to keep some fish or some plants and on the other end, the RO may have none of the needed minerals like calcium and magnesium that we need for them to do well. That may get you into using RO which removes the minerals and then you have to add them back.
So no firm answer? Tap may be good, cheap and may be far easier or RO may be easier, even though a bit of expense and bother. Much depends on how you feel about each but both have their good sides.
Personally, I hate the fuss and just adapt my tank to fit the hard alkaline water I find in most places I wind up.