I've never used barrels but I do believe that there are a lot of good things to be said for them and I may change over to them this year.  Just as an aside I think I wold prefer the molded in handles.  I've handled 55gal plastic drums with the molded in handles and they are comfortable and have enough tumblehome (for want of a better term) to get a good grip.  I would be concerned with the outside handles from several standpoints.  Dropped wrong onto the sole of the canoe the handle could cause structural damage.  The handle appears to be mechanically attached thereby causing stress points at the attachment points which will ultimately fail since the load on the rivets is eccentric resulting in a mechanical advantage.  I believe that the external handles would also be a nuisance in handling because inevitably I seem to have things like that interfere with each other at the worst possible time(blame that on Murphy).  I also suspect that some (not anyone here, ever) might actually use the handles to hang the barrels thereby hastening their demise (the barrels' that is).  Its just unnatural ;)