Is there any real difference on these barrel aged beers on draft vs. out of the bottle? If it were some hotshit IPA I'd probably choose draft, but as it is I might opt for the bottle.
yes, there is a difference. kegging beer is a gentler process than filling bottles, when done right. so the beer in the keg could potentially be in better shape. kegs are often kept refrigerated while bottles linger out in the heat.
you're right, big barrel-aged beer vs. IPA changes the equation... won't matter quite as much given this is KBS. that being said, i've had both BCBS (going for a walk soon!) and BCBSBW in both bottles and on tap, and they are noticeably different. i definitely prefer BCBSBW from a bottle.
the most important consideration, IMO, should be post-purchase preservation. bottles will last a long time. the growler will need to be drunk relatively quickly. if you're ok with downing 32 oz in the next few days, go for that - you're getting 32 oz instead of 24.