Well, that really depends on how wide a grip one takes during the two arm pull-up. Also, with the one arm chin-up (OAC)there is a much greater range of motion as compared to a two arm pull-up (both in the stretch at the bottom of the exercise, and the degree to which the upper arm can be pulled into the side of the body). In my experience using as great a range of motion as possible is key to developing strength and/or hypertrophy.
Which brings up a good point. What was the focus of the article? Since E-Dub said he found it in a muscle mag, chances are they were focusing on hypertrophy. But, then again, most muscle mags will still tell you that wide grip pull-ups are the best exercise to build wide lats.
As far as whether or not each side could potentially handle more weight doing heavy weighted chins vs. OAC’s, I seriously doubt it. Also, it’s the amount of force that the muscles in the movement must produce that matters, not necessarily just how much weight they must overcome. First realize that in order to even duplicate the amount of weight being placed on the muscles during a OAC you would need to do a pull-up with your bodyweight added (which few people can do), then take into account that the OAC requires considerably greater amounts of coordination and stabilization than a two arm pull-up. And, if you did develop the ability to add more than your bodyweight to a two arm pull-up, you would probably still get greater results from adding weight to the OAC.
Take a look at rock climbers some time. They have proportionally huge lats, and many of them routinely do OAC’s (many while holding a barbell plate in the free hand).
Finally as to whether the pecs and lats are opposing muscle groups. First, let me state that I was referring to the muscle being the prime movers in the movements. Yes, the rear delt does assist in horizontal shoulder adduction and in shoulder adduction. But, it is not the prime mover in either of these movements.
During a 1 arm dumbell row where the elbow is kept close to the side of the body, thus making the movement of the humerus primarily a shoulder extention movement the lats are the prime mover. However, if one were to reverse the movement at the humerus the action would be shoulder flexion (in which the prime mover is the deltoid muscle, primarily front head). This is not the movement utilized during a bench press. The movement utilized during a bench press would be horizontal shoulder abduction (where the humerus is out away from the side of the body) wherein the pecs are the prime mover. The opposite of this motion would be a row where the elbow stays away from the side of the body (anywhere from perpendicular to the body’s vertical axis to about 45% from it). The prime mover in this action is the traps which therefore oppose the pecs. The further away from the body the more of a pecs/traps emphasis there is, the closer the more of a deltoid/lat movement it is.