With an S corporation, revenue and expenses flow through to the shareholders in nearly the same fashion as revenue and expense of a partnership flow through to partners. There is no limit on the number of members in LLC's. Shareholders of S corporations can only be U.S. Citizens, resident aliens, estates or certain trusts. There is no such limitation with LLC's.
S corporations can have only one class of stock.
LLC's may not be so limited. Members of an affiliated group are ineligible to become S corporations. There are no such restrictions for LLC's. S corporations must make and file an election with the IRS to be an s corporation. There are no such requirments for LLC's.