I grow both and the tetraploid is indeed larger but apparently not in length of the tepals. I just went out and measured lengths and widths on a couple of inner tepals on both and found the lengths to be essentially the same but the width at the widest points are a good centimeter more on the tet form (22mm vs 33mm). The tets also have quite a bit more substance to the tepals and a sturdier stem. My regular BBs tend to flop and lean on adjacent lilies.
