The break tackle logic takes both the attribute and the player's weight into account (as well as speed, angle of the tackle, whether there are other players on him, etc). It in itself is not the exclusive factor. A small player with a high break tackle attribute can be similar to a large player with a lower break tackle attribute. Strength and size also determine how much a player will drag his tacklers, but the break tackle attribute doesn't come into play there.
That is to say, it's not a simple comparison of the break tackle vs the tackling ability to decide whether the tackle is successful.