Too many variables to make a blanket statement. When you define a relationship, we do some magic behind the scenes that allows us to anticipate some of your needs, like summary fields. So about the only scenario we can say for sure would be faster would be a single relationship with scalar data only with a summary field vs a query.
Other than that, it is impossible to say for sure. We have many situations where the queries are faster depending on the levels of relationship, amount of derived fields, whether you are using things like
now() or
user() (which are amazing, they just reduce the amount of things we can cache).
We have tons of internal test cases that run trying to compare them in different scenarios, and notably to make sure things are
staying fast, or getting faster. What I suggest, if you are really interested, is using the performance analyzer. Remove all variables except your single field and make a form with only that field on it. Then run the analyzer. Then switch your fields on the form, and run the analyzer again. That will give you the answer for your specific build.
Note that the complexity gets exponentially higher if these are used in permissions and a few other things. But the instructions above are a reasonable baseline.
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Harrison Hersch
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Qrew Legend