Hey there,
(Interviewing) experience* definitely plays a key role, however, is only one of many factors. In the end, no metric is better than the success rate of their candidates. Additional factors I would consider
- number of meetings vs. time registered on PrepLounge (shows undistorted demand)
- ranking (you can filter per firm and recommendation rate)
- the personal comments in the reviews
- normalized success rate (get a feel how it is defined, e.g., offer in B4 vs. MBB offer rate)
Plus, my number one tip to select the best coach for your needs: Write them and set up a call to discuss their
- background
- methodology
- success rate
- get some insights into the interviewing and application process for free
I offer this to every candidate that reaches out.
*This is especially true if the firm you are applying to has a very specific interviewing format, that requires a different approach than most other firms such as McKinsey with their candidate-led insights focused cases and the very specific PEI interviews that aim to retrieve fairly specific character traits of candidates. Information communicated about the McK format is unfortunately often half-accurate and that is also reflected in some coaching experiences.
For this reason, I would actually work with a coach that is 100% familiar and accustomed to a particular firm's interview style since this is where experience actually matters. In short, if you are aiming for BCG, work with an ex-BCG coach, if you are going for McKinsey, go for an ex-McKinsey coach.
If you select based on firm + follow the checklist of criteria from above + have an introductory call, you should be able to screen and select the best coach for your needs and goals.
Cheers,
Florian