In that respect OSC and mono are exactly the same, the amount of integration time needed that is. For instance:
20x180s with an OSC is a total of 1hours exposure.
5x180s LRGB is the same integration time but will be of higher quality. It will have a higher resolution due to not having a bayer matrix and you can capture straight luminance for detail and brightness.
There is no guiding difference nor any single sub length difference between mono and OSC. This is largely determined by your sky brightness (moon and light pollution), the focal ratio, pixel size and camera read noise.
NGC 6822 from my last imaging run a couple of weeks ago. This is less than two hours worth of data and the vast majority of that is just luminance (tossed out most of my colour data and half of my luminance). It could certainly do with a LOT more data but so would a OSC camera at 1.8 hours
One of the benefits of a OSC is that you don't have to worry about how many of each filter you get. I cannot comment too much on OSC imaging as I have done VERY little of it, I jumped straight into the deep end, was a struggle at times but I haven't regretted it.