Yes, the leaf shape tells you a lot. On the mature plants it's more evident. A. vaombe leaves are channeled and somewhat recurved (see picture above). A. cameronii leaves are only this way during drought stress, otherwise they tend to be pretty pumped up and lateral. Three examples here showing the changes. First photo taken during the winter rainy season, second photo in early spring as things were drying out, third photo taken in late summer after months of drought (and decapitation of the main stem).
That plant does not turn brown here (many aloes do), the color ranges from green to copper red... maybe it would behave different in the desert.
For leaf shape comparison here is vaombe (in a pot) which Thijs has noted does make less substantial leaves, broader at the base.
And for what it's worth, random sample aloe seedlings not produced using controlled pollination are more likely to be hybrids than pure species. These pictures of the actual species are only going to get you halfway to an ID most of the time. There are 500 or so aloe species out there, most of which I honestly cannot recognize.