I became an LLC in 2000 and Nelbuts is correct in that LLC's can only function as such for a period of not more then 30 years. (at least according to my formation papers which show a dissolution date of thirty years after formation.)
LLC's have tremendous tax advantages over Inc. companies as all taxable income falls to the partners, 1040s rather then haveing a corporate and then personal tax burden. As stated, LLCs offer more protection of personal assets vs a sole propriotor, provided the business is kept completely separate from the personal finances.
A quick example of separation is this, had owned trucks prior to the changeover registered to me personally. After becoming an LLC, I had to transfer title of my trucks to the LLC to separate the business from the personal. If my guys had an accident in a truck personally owned by me, my personal assets "may" have become at risk because the truck wasnt owned by the company. They are now registered to the company with a CORP code vs any personal information.
Keep in mind however, that no business formation will protect assets from intentional or gross negligence, so dont go dumping your old pesticides down the drain thinking they cant get your house.
As other suggested, check with a professional accountant and perhaps a lawyer to determine which will benefit your company most.