Mariposa, I love the Ibex Balance light bra, but it is indeed very skimpy (one layer of their thin fabric, and in my size, it really looks like a training bra ). I'm a 32 c and I ordered a med, which gave me no support, so I exchanged it for the small, which fits me much better. It's more supportive than you would think it could be, but it shows when you're chilly, if you know what I mean. I haven't yet tried it on the bike, and am not sure it will be as good as the Bralette for commuting.

The Bralette is less skimpy (2 layers of fabric), but also not enough to hide much under a thin t-shirt, for example. If you wear thicker tops than that, the Bralette will probably work well for you. I think it would be fine under a tailored shirt.

I tried the sports bra, and I found it much too high in the neckline, so I didn't keep it.