20 is a boring mechanical bump. Boring mechanical bumps do not feel large even when they are.

There are going to be some feats which may matter more. Are you a twin casting haste sorcerer? Then advantage on con saves for concentration might win.

But the baseline "AC" for saves is 14; a +5 mod means you can become 90% reliable hitting 10 stat no save targets. And on +6-7 prof tier targets it means your spells eat through legendary resists that much faster.

You can build for "do not trigger a save", but that is going to be restrictive. I've done it.