Well way I see it thus far is if we look at just the legal aspect two words come to mind. "Avoidance" and "Complexity". If I were looking for a black and white answer or some logical reason to form a LLC as Reed says not going to happen as with most law. So to avoid court create as much complexity and avoidance as possible. As we learned it is more difficult to pierce the corporate veil of an LLC that has multiple members and shareholders with complex operations than of a single member-owner-manager with single operation such as land lording. As Reed said, legally bound contracts to the LLC written properly by competent attorneys is "ironclad", makes sense, more logic, more black and white, and I would extend that to the Operating Agreement. Very important stuff!
As for the average REI that thinks they can take such a complex area of law write the OA and contracts themselves, I'd venture to say for the single owner LLC doing only tenant-landlord law and/or flipping the LLC is not worth the paper it is written on and you wasted filing fees at a minimum. A SP would be just as effective maybe more saving legal fees to get out of a mess for one.
Steve, you're further along than I am. I'm start up doing prelim research, looking at a construction company that also invests in RE down the road which may have employees and other complexities, or operations, risk, to make a LLC more appealing. Way I see an LLC now is an illusive firewall between me and a lawsuit, but that may change as I learn more. A legal persona or scare tactic if you will, bullet proof if I find no other way (insurance, etc) to hiring a good attorney spending the money to create ironclad contracts to an LLC or myself(sole propriety) for that matter. Meaning for example, if I were just land lording or somethng simple like that rather than create an LLC I might consider finding a good landlord-tenate contract (or attorney to write one) that releases me of liability to the max extent of state law. I'd find out what that extent is look for it in contract and with an attorney, then stay SP keeping the maintenance up on my properties and avoiding potential law suits. Hide assets and insure them. It would be nice to contract bank loans to an LLC, but as Reed said probably not going to happen until it has assets.
So to answer your question, I don't know yet. I plan on going back over Reeds article and try and apply as much black and white logic as I can to my business plan and requirements then make an educated decision to the best of my ability knowing that can change based on my business model or say five year plan. What I mean by that for example is in the form of legal complexity and assets I could decide in the beginning to go SP and as I gained more legal complexity with employees, stock, assets, partners, etc, form a LLC.
My .02.