I’d agree with you to a point, much of it depends on the surface area and efficiency of the condenser itself, and the relative vapor pressure at hand.
Many people use rotovaps, and the glass is just terribly inefficient, so in the cannabis space with glass In mind, I’ve found a “delta 20” to be inadequate for solvent recovery in general.
I suppose we should ask for more info from OP on how he’s recovering to see what makes the most sense.
Provided we’ve got efficient surface area to condense with you’re definitely right, but across a bunch of real world applications I find I’ve needed to get minimum 30c delta, if not higher.
I tend to also set things at a 40+ degree delta, and by the time it’s actually running it’s tighter too once the chiller is under load.