Tavern = neat stuff (updated version of visions of insanity AKA free stats for whenever you dont want to waste flasks, an epic follower, toys etc), and a free lvl 90 follower with a specified trait/ability every week.
Barn = raid feasts and small chance for savage blood to upgrade crafted gear.
If you've got the money to spend on SB, there's no point in the barn on a main. Alts can keep you stocked with raid feasts (just 5-10 raiders has a lvl 2 barn going 24/7 you'll never run out of feasts).