I'd say you have to choose the agent, not the company.
The agent should provide you with a great marketing plan and international exposure, if applicable.
There are many ways to market a luxury/corporate rental property - through relocation companies, Furtune 500 companies and their HR, blogging, all real estate sites, glossy magazines, other brokers network, neighbors and so much more!
You got to really understand what specifically will be done and when, and the most honest agent
should be picked to do this job.
I don't believe in using large corporate outfits as they often limit agent's creativity in marketing.
With the right marketing budget, a good agent will get anything accomplished for you.
Hope this helps,
Beachfront Realty, Inc.