The rally that has made the energy the best-performing sector in the current quarter and second-best year-to-date has not been led by integrated oil giants such as Dow components Exxon Mobil (NYSE: XOM) and Chevron (NYSE: CVX).

Nor has the sector’s upside been confined to just one industry group. Rather, bullishness in the energy patch has been widespread, including multiple industries such as oil services. Over the past three months, the Market Vectors Oil Service ETF (NYSEArca: OIH) ranks as one of the best sub-industry ETFs with a gain of 15.6%. The iShares U.S. Oil Equipment & Services ETF (NYSEArca: IEZ) has not been too shabby either, gaining 14.1%. [Oil Services ETFs Take Leadership Role]

Although it has trailed OIH and IEZ, the SPDR Oil & Gas Equipment & Services ETF (NYSEArca: XES) should not be ignored as alternative or complement to its rival oil services ETFs because XES employs an equal-weight methodology that has proven successful with energy funds. [Equal-Weight Energy ETF is a Winner]

A familiar criticism of OIH and IEZ is that these ETFs are really proxies for two stocks – Schlumberger (NYSE: SLB) and Halliburton (NYSE: HAL).The average combined weight to those two names in OIH and IEZ is about 33%.

Conversely, the top-two holdings in XES – Weatherford International (NYSE: WFT) and Superior Energy Services (NYSE: SPN) – combine for barely more than 5% of the fund’s weight. Halliburton an Schlumberger are top-10 holdings in XES, but combine for just 4.9% of the ETF’s lineup, according to State Street data.

Spending on oil services is on the rise, a positive for all three ETFs highlighted here. Earlier this year, Barclays forecast an industrywide capital spending increase in the U.S. and Canada of 7% following two years of spending growth below 5%. [Plenty of Catalysts for Oil Services ETFs]