I actually had to study a little bit of business law when getting my master's degree. The following is taken from Barron's Business Law book (2004) and explains the differences between an LLC and S Corporation. There are subtle differences and these may change from state to state, so its best to consult an attorney and possibly an accountant (for tax reasons) before making a final decision.... Also, if you look at the 2nd paragraph, it appears that some states do not allow professionals (PE's) to form LLC's, so that may not even be an option for you. Good Luck!
"To some degree, the LLC format is replacing the S corporation format. The LLC is similar to an S corporation (e.g., as with partnerships, no double taxation; as with corporations, limited liability of members/shareholders), but has advantages over the S corporation because it is more flexible. The LLC has (a) no limit on the number of members/shareholders (only 75 are allowed for an S corporation); and (B) nonnantural persons (e.g, corporations) and foreign citizens can be LLC members (the fules are more restrictive for S corporation shareholders). Nonetheless, compared with partnerships or corporations, there are some potential problems with LLCs. First, although both partnerships and LLCs are not subject to federal income tax, LLCs (as are S corporations) are sometimes subject to a state income tax (e.g., in Florida and Texas), which partnerships are not. Second, an LLC may not be permitted to merge directly with a non-LLC. Therefore, the only way to effectuate a merger is for the LLC to dissolve, for a corporation, merge with the other entity, and then revert back into a LLC, with each business format transformation tending to create tax liabilities. (Conversely, corporations generally can merge without undergoing a dissolution.)
Legal Analysis, though, must be tentative: LLC law is still new. The legal principles often are uncertain both within a state and across state borders. For instance, some states tax LLCs as if they were corporations (a few states do the same for S corporations), and some states do not permit professionals to form LLCs. Additionally, an IRS regulation promulgated in December 1996 permits most business entities simply to "check the box" and choose whether to be treated, for federal tax purposes, as either a corporation or a partnership."