Ask a computer scientist and a biologist how to judge a venue and you'll get two different religions. Both are correct, for their field. The trouble starts when you apply one field's metric to the other's venues.
CORE rankings measure conferences. They exist because computer science publishes mainly at conferences, which is unusual. Most other fields publish in journals, and for them the journal impact factor, or the Scimago quartile, is the prestige currency. Neither system was built to judge the other system's venues. Using one on the other is like grading fish on tree climbing. People do it constantly.
So which do you trust? The one your audience uses. Hiring committees, grant reviewers, tenure panels, they all read the signals of their own field. A CS committee knows exactly what a CORE A means and will shrug at an impact factor. A biology committee does the reverse. Publishing is communication, and prestige metrics are part of the message. Speak the local language.
Interdisciplinary work is where it gets interesting. An AI-for-healthcare paper could go to a CORE A* ML conference or a Q1 medical journal, and those two audiences barely overlap. There's no right answer, only a strategic one: which community do you want citing you for the next five years? A journal and conference ranking database search tool that covers both systems lets you compare top conferences by discipline against journal quartiles on one screen, instead of arguing from memory.
One more thing. Both systems get gamed. Citation cartels inflate impact factors. Reputation surveys lag reality. Treat any single number as a noisy signal and triangulate: tier, citations, and whether people you respect publish there.
Compare both systems side by side at confjournal.fyi, with CORE tiers and Scimago quartiles for 329 venues in one database.
When the paper is ready, confjournal.fyi will get it submission-ready with paper formatting and submission checks for your target venue.