SMC is the general name for the approach; ICT is one particular school inside it. The relationship is roughly that of "technical analysis" to a single author with a notation system of their own.
So the question "which is better" is put wrongly: these are not two methods but a category and a case of it.
What they share
The foundation overlaps almost completely: market structure, breaks on a close, pierces of levels, gaps, zones a move started from, a range split into upper and lower halves.
Strip the names and leave the objects, and the markup comes out alike down to the details.
Where the glossaries diverge
The same object often has different names, and that is the main source of confusion.
A gap between the wicks of three candles is an "imbalance" in the general vocabulary and a "fair value gap" in ICT's. A pierce with a return is a "liquidity sweep" or "stop hunt" in one place and a "judas swing" in another. A zone a move started from is an "order block" almost everywhere, but its boundaries get drawn differently.
The reverse happens too: one name for two different objects. Check by the description rather than the term.
What ICT has that the general vocabulary does not
This school does have a distinctive part, and a substantial one: an attachment to time of day and sessions, dedicated names for specific setups, particular daily and weekly templates.
Importantly, the time attachment is an independent assumption. It rests not on chart geometry but on the claim that certain hours behave differently. Verifying that takes measurement rather than markup, and the measurement has to be done per instrument.
Where the confusion arises
Taking an ICT term for a standard. Someone reads about a "kill zone" and looks for it in the general SMC vocabulary — where no such concept exists.
Assuming different names mean different objects. Most often it is the same thing from different sources.
Comparing markups without comparing rules. Two people with different definitions of a break get different pictures from one chart, and the argument is about vocabulary rather than the market.
The practical takeaway
Learn the objects, not the schools. Once structure, pierce, break and zone are clear, any glossary reads in an evening — and it becomes obvious that behind a new term usually sits an object you already know.