I agree with this to a point. I think first you should master stability and then introduce controlled instability. I do think that a lot of people shoot themselves in the foot by keeping things too stable for too long, corals that are kept in somewhat varying conditions usually don’t react much when a parameter is off, whereas corals that are kept in exacting conditions can full-on RTN if the salinity is a little off. The trade off I guess is that usually only corals that are already well adapted/acclimated to tank life will thrive in controlled instability. Also, I think it’s important to note that while corals do experience hourly, daily, and seasonal fluctuations in the wild, that doesn’t necessarily mean that is what is preferable in an aquarium. It’s in an interesting discussion, but I think ethically, you have to understand reef chemistry and how to control it before allowing some controlled instability. Flying by the seat of your pants without a working understanding of how a reef tank works chemically and biologically, is just irresponsible, instability can be a positive thing in a tank, but it has to be controlled.Stability is overrated! Wild reefs are not stable! Especially not for 90% of the corals in the trade which come from shallow lagoons and flats. They get blasted with rainstorms frequently which absolutely swings salinity quickly. Cold upwellings come into reefs all the time not to mention the highly seasonal variation of places like lord howe island! pH swings happen in the wild too for various reasons. In many places, all sorts of corals, yes even freaking acros, bake in the hot sun for several hours a day out of water.
I think "stability" really doesn't matter to hardy corals like the ones you're likely to keep in a pico anyways. I am not sure it matters even to the "difficult" corals (within reason)
The most difficult part of reefkeeping is long term consistency in maintenance. A pico is very easy to clean and garden in. I'd bet on success for 5 well kept gallons over 50 gallons of lazy.
If OP wants a pico get a pico. It's small enough that if you regret it starting over isn't the end of the world anyways.