Coming at this rather late too and just have one comment - I think there are some sweeping generalisations and the culture within a firm is not necessarily something you can determine by the size of the firm.
I, my H, my sister, my Aunt and most of my cousins and their partners are lawyers. We range from equity partner, salaried partner, Of Counsel, associate and newly qualified solicitor our family get togethers are a riot (not!)
I have worked at large regionals for 14+ years and have never been actively involved in billing, chasing payment etc. Just recorded my time and someone else prepared bills (which I signed off) - we were generally working (a number of solicitors) on big transactions / large clients. Did have to do general business development but most of our work was won by tender / on service agreements so there was no scrapping around for work. Ever. I think it depends on what area you work in, how the head of department works. Yes, I had to be aware of my hours and my fee target but certainly at a solicitor level, even at associate level, it was the partners / BD team that brought in the work and there was no pressure on junior solicitors to worry about finances etc. I disagree that you won't do any "law" work at a large regional - that's all we did. I am now at a smaller firm and I would say yes, there is more "business awareness" about profitability, fee generation, but I would say 90% of my time is still giving advice / dealing with the "law". The other 10% is BD and admin.
And I also disagree that only magic circle / City firms have people who are the best of the best. There are an awful lot of genuinely gifted lawyers who work at large regionals and are respected leaders in their field. They may have been in London for a time, they may have never worked in London at all. Having socialised with some of my sister's magic circle friends, its not a given that you'd be good at what you do just because you're in the City
. Certainly as a trainee, my sister spent a large proportion of her time on what I would call admin (photocopying / proof reading, collecting the partners dry cleaning ). Definitely less opportunity for "learning" at a MC firm (IMO).
My H is in a tiny high street practice. He is fighting people off with a stick he is that busy. He works more hours than I do. He earns about the same as I do (high for a high street firm) because his firm knows how valuable he is. Again, aware of his target etc but hasn't got time to worry about debt collection/ bill payment. Even in a tiny firm they have a cashier / accounts person to deal with this.
I think as this thread demonstrates, the firm's culture can often be dictated by the partner you work for, or the head of the department. Yes you can make some generalisations about hours / training contracts / likely pay but honestly, teams / specialisms / firms can be vastly different and you'll only get a feel for a particular firm if you get the chance to work there. There is lots of "snobbery" - not the right word - about London firms having the best lawyers / clients / quality of work. It really does depend on the specialism and the firm. Good luck whatever you decide.