The most important argument IN FAVOR of a built-in cooktop, in my view, is that pots – and everything else – can be slid back and forth on the surface without a step.
I have a stainless steel countertop (with chipboard underneath) and a built-in Miele cooktop. I filled the joint myself with special silicone and except for one – non-dramatic – flaw, it is completely fine. Miele claimed to still have the same cooktop sizes even in many years. Whether that will work, I don’t know. If it turns out differently, I can either choose a larger cooktop and adjust the cutout (I think that should be technically feasible), or place another stainless steel plate on top and either place the new cooktop on it or fit it in. Not "really fancy," but definitely doable.
It’s clear: most of these problems don’t exist with a surface-mounted cooktop. (but then you also don’t get the advantage mentioned in the first sentence of this post)