However, performance indicates that size matters. Nine out of the Alerian Index's top ten constituents enjoyed price gains in 2011.  And five of them turned in total returns of more than 20%.

Sean Wells, an analyst at Steelpath Advisors, an industry specialist with $2.1 billion under management and which manages several open-end MLP mutual funds, believes that partnerships with market caps over $8 billion to $10 billion are generally less volatile than smaller ones. "Their steady performance," he explains,  "comes from more diverse assets, more fee-based income, less commodity exposure and higher credit ratings that allow them to finance expansion at a cheaper cost."

FA Mar 2012 MLP fig 2

MLPs