Avantages
RXP have almost universally great consultants. They also have really interesting and well known partners. Strong growth and demand for junior and mid level consultants. Good training for new consultants. While I have no experience personally working for their direct competitors (UXC, SMS, DWS, Infoready, etc.) my colleagues suggest RXP compares well against them.
Inconvénients
Not sure the RXP maxim of 'specialism wins' is actually true, at least not for RXP. I found my technical skills eroding over time as I was asked repeatedly to perform roles outside my domain - because the sales people struggled to identify clients a projects with my specialisms. No training offered in my domain even when asking for specific relevant courses or certifications. For senior/principal consultants, as there is not technical career progression, there appears to be no value in being an employee - if you are on the bench you are likely to get fired. Lack of security means you will probably be better off as a contractor. While ostensibly RXP compares well to it's direct competitors, the business model appears identical and I can't see any current advantage being sustainable over the medium to long term.