Let's go with a "White-to-White" Burst scenario to argue which is the better "Burst Weapon"
Glacial Stone procs for 75 damage, is 3.6 Speed and has the same base damage range as the BAR, which is a 3.8 Speed weapon with some strength.
In order for the BAR to exceed the GS's burst potential in a "White-to-White" Burst combo that includes a GS Proc, the BAR would need to deal more than 75 damage more than the weapon hits from the GS. Measuring with white hits alone, this would require a 37.5 weapon damage range advantage over the GS via the 0.2 speed difference. In order to do this, you'd need to have 187.5 DPS from AP... or 2625 Attack Power. I'd go for the GS for the purpose of burst potential, however, the stats on the BAR help make crit combos a little more consistent.
Now I'm not gonna calculate the bonus damage gained from STR on the BAR would make on the two white hits + any additional attacks you slip between the two, or the additional effect the .2 speed would have on the Paladin Seal, but it should have an effect at reducing the AP requirements to trump the GS proc in Burst Potential some.