As Clownfish2 mentioned, stability of parameters is everything.
The advantage of doing a Softy tank vs SPS is if you have a *temporary* problem with your water the Softies will usually recover instead of dying out completely.
Otherwise they are almost as demanding as SPS.
One nice thing about most softies is not needing a lot of dosing if you do regular water changes.
The SPS suck minerals out of the water to build their hard skeletons. Those minerals need to be constantly replenished with dosing.
We have a 75 gallon tank with 200 pounds of live rock and just 2 MarineLand 400 HOB filters.
The 200 pounds of live rock does most of the biological filtering.
I add Phos Xtrax to screen containers for the HOB filters and change them every week or every other week depending.
(The white beads work better than GFO in the screens.)
Weekly water changes of 10 gallons and thats it.
I work out of town occasionally and can't (lol, not allowed to) have plumbing problems while I'm away.
So no automatic top off, dosing pumps, etc. Everything has to stay pretty simple and manual.
I add a half gallon of RODI water for top off almost every day.
(Or water change and 3 gallons RODI when I get back home...) We keep salinity around 1.022 at full top off so it only creeps up to 1.025 by the time I get back in town.
Can you tell us about your tank?
Size, lighting, water changes, etc.