They are both great for archery spike elk. The deer on the Fishlake are not as big as the ones on the Boulder on average in my personal opinion. However, the boulder is one big world. I like the area from Posy Lake to Roundy Reservoir on the boulder. You really just need to get in there and discover the area for yourself. The guys who do good have hunted it for years and that is why they are all hush-hush about their honey holes. I don't know Fishlake as well, but there are a ton of elk on both of these units. Good Luck
Dillon