Separate the checkable from the judged
Licence number, category, and register status are facts with a right answer, independent of how any conversation with an agency has gone. Run this check identically for every agency on your shortlist before weighing anything else, since a Category A licence or an unlisted licence number removes an agency from consideration on structural grounds alone, not a matter of preference.
Everything past that point, fees, guarantee terms, communication style, timeline, is where your own judgement actually applies, and that’s fine; the goal isn’t to remove judgement from the process, it’s to make sure the facts you’re judging are actually comparable.
Ask every agency the same questions, in the same format
Request an itemised fee breakdown, the exact wording of any guarantee or replacement term, and an expected timeline from each agency, all in writing. A comparison built from one agency’s detailed written quote against another’s brief verbal summary isn’t actually comparing the two agencies; it’s comparing how much effort each one put into answering you.
Once you have the same categories of information from each agency, in writing, the comparison itself becomes straightforward: you’re looking at the same rows across different columns, rather than trying to compare fundamentally different amounts of detail.