It's never purely about the money. The thing about joining small firms it that it essentially means tying your career development to the principal lawyer of that practice.

The questions to ask are always: has the principal lawyer built a stellar/good reputation in his area of practice? Is he known to be a good boss? Does he pay well (only 1 of various factors)? When it's time to leave for my next role, will having known to have worked for him, prove to be a boon or a bane to my CV?

These are all principles of general applicability when choosing to join small firms where the branding of the practice isn't institutional, but is intrinsically linked to the principals there. I'm in no way making any comment about Fervent Chambers in particular. Just my general thoughts.