Compare GDXJ to GLD. look at 2 yr, 1 yr chart clearly shows underperformance. However, when you look at 6 month chart, it shows GDXJ has bigger moves top to bottom. It outperformed GLD at the top significantly. Look at 1 yr chart tells you that underperformance over the last 5 years already priced in. Miners will simply exagerate movements over GLD. If you want to pick a bottom, miners has more bounce.
IF you pick the bottom successfully. The one year chart shows gap between GDXJ and GLD at 15% when gold was at October high. Today the gap is 35% . This gap could narrow significantly when gold rallies. Expect miners to outperforme in the next rally.