Running the numbers you gave, the 162 ELDX is 1.34 stable on the Berger calculator. This is fine. Berger used to use 1.4 as the cut off line for bullet stability, but changed it to 1.5. At 1.34, you are fine for stability, but the BC will be slightly reduced.
On the 180 ELDM, I'm showing 1.3 stability factor, with a 6% loss of BC. This is still fully stable, just not as stable if you were running a 1:9" or 1:8" twist. But, with the super high BC of 180 ELDM and a 6% loss of BC, it's still a better option than a 162 for drop and wind drift at longer ranges (700+ yards). If you will be primarily shooting inside of 600 yards, I'd lean tot he 162 grain. If you are wanting to shoot majority of distances further than 700+, the 180 would work well.