No clue about seal, but will say that the Rembrandt whitening toothpaste with peroxide is much better!
Everything I've learned has told me one toothpaste is as good as the next...as long as it has fluoride in it. The very short time the peroxide is on your teeth prevents any real clinical whitening to occur.
As a professor once said, you could brush with water, as long as it has a proper amount of fluoride in it. The rest is just to make your mouth feel and taste better, while doing nothing in terms of decay prevention and/or whitening.
edit: a quick Google Scholar search yielded this, which does show a whitening toothpaste removed
stain better, while not necessarily whitening: http://cat.inist.fr/?aModele=afficheN&cpsidt=13934984
I guess there is a little benefit.