Are state owned enterprises really inefficient?
SOE's don't have to perform worse that private enterprises, but they often do.  The reasons are manifold:


Some SOE's are not set up for profit motive, but rather to seed strategic industries for a nation (e.g. Port of Singapore, or Huawei Telecom).
Frequently, state influence at market-oriented is counterproductive because politicians placed in leadership positions are not good business managers (different skillsets), and political contacts can have a detrimental effect on competitiveness (overreliance on government contracts, etc).
Even if the SOE is run by market-selected managers and employees, states often have different shareholder incentives and objectives as owners, so they may not exercise market-driven ownership which leads private firms to attempt maximizing equity value and earnings.


Note that it's not true that SOE's are not funded directly by government.  Many SOE's receive partial funding through government, and many others receive heavily subsidized contracts from governments.

There is quite a lot of research on SOE performance.  Do a search.  For example, McKinsey did a study on Chinese SOE's and concluded that on average they deliver less than half the return on assets as their public counterparts:

http://www.forbes.com/2004/11/04/cx_1104mckinseychina6.html