Outsourcing is a business that trust is the first requirement. Business won't grow if you haven't trusted the company that you're working with. This business has it pros and cons, you just need to find the right company, ask for samples and client references so you can decide. There are lots of outsourcing providers who pretend to be the best, that's why you need to be careful and look for the reputable ones. I suggest to hire a Staff leasing company instead of a freelancer. because leased staff are permanent workers of a company and are easy to reach in case you need them. Freelancers do not have employers so they do as they please and sometimes cannot be contacted for various reasons.
Th first option is the better choice since it is more cost effective and you get experienced people to do the job for you.
If you can get folks who you trust and can train them it would be the way to go. In fact this is how many Internet Marketers outsource their work, by training the staff to ensure they know what they are doing
For maintaining SEO business I think fulltime is the better option to choose. Because in SEO business your client's site may be affect by Google Panda due to not being pinged for long time if you choose a freelancer as he or she will boost up sites very professionally but not for long. So...............