It really depends, I'm sure that is what you were wanting to hear :)
It depends on the specific relocation package for the Seller, how long it has been on the market, how much activity they have had, how much or often the price has been lowered and a few more things.
The biggest benefit I've experienced is that relocation companies don't want to own homes.
If you have identified a home that is 'owned' by a relocation company my experience has been that you will be able to negotiate a better sale price than with a typical home owner. (keep in mind, this will vary for every situation).
The drawbacks include a slower negotiation, tons and tons of disclosures and waivers of rights, less contact with the Sellers, and more.
Good luck!