Out of position in BB with top pair and weak or middle kicker I almost always checkraise since you know the CO will bet the flop. You can't really protect your vulnurable hand by betting out and you really want to reduce the field. The preflop raiser was in late position so there is a good chance you will be able to get it headsup. It also provides more info as if he reraises your check raise you can slow down.

edit: and I'll add that a checkraise would have made the turn decision alot easier