The iPath Dow Jones-UBS Natural Gas Total Return Sub-Index ETN (NYSEArca: GAZ) and the United States Natural Gas Fund (NYSEArca: UNG) are each down about 2% in midday trading Thursday, but that does not change the fact that the two entered Thursday’s session as second- and third-best non-leveraged ETFs this year.

At the start of trading Thursday, GAZ and UNG had an average year-to-date gain of 25.2%. UNG, something of a household name among commodities ETFs, has been criticized over the years for high fees caused by the ETF’s rolling of futures contracts. That situation worsens when gas is in contango, or that scenario that occurs when longer-dated contracts are pricier than near-term equivalents.

Criticism not withstanding, UNG does what it is supposed to do. In years past, that has not always been a good thing. This year, UNG and GAZ merely doing their jobs has worked quite well as the polar vortex that swept over much of the Midwest and Northeast led to colder temperatures and increased gas demand. [Nat Gas Tops $5]

Not all ETFs are benefiting and that sentiment is not confined to inverse natural gas funds. As GAZ and UNG have soared, the equity-based First Trust ISE-Revere Natural Gas Index Fund (NYSEArca: FCG) has been a noticeable laggard.

“With the surge in natural gas prices one might have expected the equities that focus on this sector to have also benefitted but that really hasn’t been the case with FCG currently down just over 1% for the year. While it has shown decent relative strength versus the overall markets current 5% year-to-date loss it has not had the price appreciation one would have hoped for with the commodity’s big move,” said Al Sabogal, former head trader for Perry Capital, in an email exchange with ETF Trends.

FCG will turn seven in May, so the fund has been around various treatments of natural gas. It surged alongside with natural gas futures in 2007 to the commodity’s peak in the second quarter of 2008. FCG would then proceed to plunge alongside gas.

To FCG’s credit, the $458.4 million fund has been significantly less bad than UNG over the past three years. Dating back to 2008, FCG has only been outpaced by UNG once on an annual basis, but that is in the past. With UNG and GAZ soaring this year, FCG’s lethargy is vexing for investors. [Warm Winter for Nat Gas ETFs]

Sabogal highlights several reasons why FCG has been left behind in the natural gas rally.

“At the end of the day FCG invests in equities and with the pressure we have seen on stocks this year the etf is not immune to the risk off dynamics we have seen in the overall market,” he said. “Investors may be skeptical about the duration and sustainability of high demand for the underlying commodity…the polar vortex made for a harsh winter but spring is just around the corner.”