The really large ones like EPD, KMP and ETP are pretty much all the above now. Each has their own concentrations but only EPD was first to focus on liquids. Beating even Mr. Kinder on that one.
PAA is also branching out but they do more delivery of finished products.
So perhaps today it is more a matter of whether it is a large foot print diversified pipe or a more regional pipe defined by the resource developed in their locality.
EPT has some long haul natural gas pipes up into New England which no longer have a reason to exist. However, they are converting those pipes to oil or liquids now. They are also trying to do the same with a gas line in the MW no one needs. So right of ways while difficult to value are important.
There are many MLP pipeline companies. Your best bet is to check out the company website to see which process they are manily involved - some are gathering/processing, some are "long haul" but they may also own processing stations.
Some examples are: Boardwalk Pipeline Partners (BWP); Buckeye partners (BPL), Enbridge Energy (EEP); Energy Transfer Partners (ETP); Enterprise Products (EPD), Kinder Morgan (KMP/KMR); Magellan Midstream (MMP), Nustar Energy (NS); Oneok (OKS); Plains All American (PAA); Spectra Energy (SEP); Williams Partners (WPZ).
Gatherers/Processors include: Atlas Pipeline (APL); Copano Energy (CPNO); Crosstex Energy (XTEX); DCP Midstream ((DPM); Eagle Roak Energy (EROC); Markwest Energy (MWE); Regency Energy (RGNC); Targa Resources (NGLS) and Western Gas (WES).
Then there are companies that do exploration and production, but also own pipelines: Linn Energy (LINE) has a small network of pipelines; PVR Partners (PVR).
.Of goodness. Trying so hard and blowing it still.
EROC just a gather processor?
Markewest just a gather processor?
EPD with the ability to move product around their system and arbitrage localized pricing is just another long haul because they have some long pipes?
LINE is now a 'pipe' company because they own their own gathering system so can decide which pipe they tie into? Of course no final determination of the HUgoton assets.
By RLPs thinking Walmart is a pipe because it has natural gas service.
Every one of these MLPs are very different businesses. RLP does not understand but that will never stop it.