Simson- ERC is the heaviest juniper I believe and has the most heart to sap ratio of junipers. Mountain juniper is the California juniper and the juniper used by Ishi. This is Rocky mountain juniper, grows here in Utah along with Utah juniper. It's no wonder why Junipers was so popular in the Great basin, Plains, eastern California, and the Columbian plateau. It's no yew or osage, but still somehow my favorite.
Gabe-- Still mostly make short bows, but sometimes it's nice to be able to get more than 2 out of 5 arrows in the center of a target from more than 20 yards. Longer bows have a lot of advantages when your off your horse and I think almost everyone on this site understands that.