Here's my .02
IO will provide you with the basic nutrients for successful growth.
If your tank is lacking a certain supplement, it is far easier (and cheaper) to add that specific nutrient with dosing.
That being said, if you use RC, you guarantee that you will be adding X amount of nutrients with every water change, and in most cases, you don't need all the nutrients that the RC is providing, thus leading to an overabundance in a certain nutrient.
From what I have heard in person.. it is far easier to add the nutrients you are lacking via dosing, rather than taking out all the buildup of stuff you don't need.
Plus RC is like 2X the cost of IO.