It's very difficult to tell if the Switch is off or in RCM, and a lot of people drain their batteries by accidentally leaving the Switch in RCM. In addition, if someone comes along and tries turning it on, even if it was powered off properly, it will boot straight into RCM.
The Switch was designed to be kept in sleep mode indefinitely, and as you read, it is marginally better for the battery than leaving it in a powered off state.
The only time to power off the Switch is if it's not going to be plugged in and/or docked for a very long period of time. If you keep the Switch in sleep mode when it's not being used, you are a lot less likely to run into issues than if you power it off.