Pros
As co-founder of the company, please take my review with a grain of salt. With that said I hope this is a (relatively) accurate view of the pros and cons, said in a not at all marketing oriented way. Not at all ... Some pros - as a young company there are a lot of opportunities to contribute and grow - and with that growth we've been pretty good about salary increases. We are very focused on culture and being a great place to work, and hopefully we've done that so far. Work life balance is excellent for an IR company. We have and hopefully always will have a relative lack of "consultancy politics". All these pros are reasons we started the company in the first place and it genuinely matters. We are doing some interesting work around automation, and are always open to new ideas. Last pro - nobody has ever resigned or been fired. It will be a sad day when this happens, but it hasn't yet!
Cons
The structure is less than what you'd find in a larger company. As an IR company, we can get busy at times (but I think we are very good overall at managing this!). Our engagements are mostly focused on small to mid sized clients so very large engagements are rare, although we've done some pretty complex state sponsored attacks so the tech side is still interesting.