The real strength of Stratified living standards isn't just that you can save on CGs, but that you can totally mistreat your non-Ruler pops, throw them all in chains (Indentured Servants can do all specialist jobs), and your stability will still be fine because the Rulers have virtually all the political power. Conquered worlds can be easily stabilized by bringing in a few primary species pops to rule over them. Now that Merchants are spammable, you can easily adjust the number of Ruler jobs on the planet to suit your stability needs. If you're not Authoritarian, then Decent Conditions does a similar job, but not as effectively.
If you don't intend to mistreat pops and just want to make everyone happy, then indeed the more equal living standards may be better. Shared Burdens specifically though isn't very good value for money unless you have a huge proportion of Ruler pops. For more normal proportions of pops, the non-ethics-restricted Social Welfare often works out better, giving twice the happiness and better passive trade income for only marginally higher CG upkeep. It's also something you can apply selectively to subspecies or transition into as the proportion of Workers in your empire goes down, as opposed to being locked into it from the start. Decadent/Utopian living standards are of course more powerful, but the former requires a civic and the latter is quite expensive CG-wise.
