Wonder failgold is much stronger than wealth, yup.
(if resis are available, and / or IND).
Slavery, overflow hammers & chopping are very important when considering "economy builds".
When we look at how many hammers 2 chops i.e. into a marble wonder create, at least 120 (with maths), lots of gold once they are completed.
With whipping & overflow, builds can be done without hammer tiles used, and that city can still contribute (fail)gold
Wealth & research can be very good to store hammers.
We can even use the failgold example, if waiting for wonder techs or maybe resis connected (marble or stone further away, and workers not ready yet?),
forests can already be chopped and those hammers kept by building wealth / research.
When everything is ready, all hammers created show for wonder building.
Original question, i only use research "builds" if i have enuf gold for both 100% slider and cities on research,
and want to reach a very useful tech quicker.
Examples could be Civil Service, Bur. usually pays back fast (so we can say cities on research created those beakers + what x turns of Bur sooner give).
Or when running a golden age, and it's close with reaching Civic unlocking tech(s) while they are still Anarchy free.
Overall building research can be used for urgency situations, but only if gold allows 100% slider (explained by others already
).
Wealth can be seen as creating gold that's needed now, not in x turns like failgold, or if there's nothing else, and as hammers storing placeholder.