There is no shortage of gold miners exchange traded funds from which to choose, but the two with enviable brand recognition are the Market Vectors Gold Miners ETF (NYSEArca: GDX) and the Market Vectors Junior Gold Miners ETF (NYSEArca: GDXJ).

Up 18.2% and 28.5%, respectively, GDX and GDXJ are two of the top-performing industry ETFs this year, but as their names imply, there are important differences between the two funds.

While GDX offers a mix of small-, mid- and large- capitalization stocks, the $8.1 billion ETF is heavily tilted the largest gold miners. For example, Goldcorp (NYSE: GG), Barrick (NYSE: ABX), Newmont Mining (NYSE: NEM) and Silver Wheaton (NYSE: SLW) combine for about 40% of the ETF’s weight. On the other hand, GDXJ is more of a bet on potential. [Miners ETFs Ready for a Rally]

“There’s much more speculation involved in the GDXJ as that whole ‘potential to generate’ gives them a lot of leeway when they choose what stocks they’re buying for that ETF,” notes Cody Willard for MarketWatch.

To be sure, both GDX and GDXJ are momentum plays that can provide traders with big moves in condensed time frames. Traders that are familiar with GDX and GDXJ know it is not unusual for these ETFs to post intraday moves of 3%, 4% or even more. And the pair have been particularly action-packed in recent weeks as gold has rallied.

Over the past month, the SPDR Gold Shares (NYSEArca: GLD) is up 5.3%, but GDX is up nearly triple that amount over the same time. GDXJ has almost quadrupled GLD’s one-month gain. [Investors Flock Back to Gold ETFs]