Area Director of Housekeeping at Vail Resorts
I have personally worked with a couple of third parties in the past, one that managed only the hiring process and the payroll portion, and one that actually managed the operations - under my team's supervision.
I don't think it's fair giving an opinion based only on two precedents, but I can share I remember my experience when outsourcing operations as a challenging one.
There are certainly benefits from choosing to go this route: number one undoubtedly is the hiring and paperwork process, which agencies are specialized on and have all the necessary tools and connections to be able to make it happen quickly and efficiently. A small company or an individual property would not be able to keep up with all the documentation necessary to bring in lawfully and maintain a foreign worker in housekeeping.