Both pics look like the same plant to me :-) One is just larger, more mature and appears to be receiving better care. True Aloe vera has fleshy, succulent leaves with no defined stem, a pale green or gray-green color and is often spotted. Leaves are marginally serrated and with short white 'teeth'. Under good conditions, will produce a tall flower stalk in summer with a cluster of pendulous yellow flowers at the top.

There are about 400 species of aloe and some look quite similar, in fact several species are considered to be nearly identical to Aloe vera, only set apart by a different growing area/range.

But the bigger one has always been in a rosette shape even when it was young and the small ones always grow parallel, heres some better pics.

http://luvcosmetics.com/the-benefits-of-aloe-vera-skin-care
http://www.ivy-rose.co.uk/Health/Articles_Images/Aloe_Vera_w300.jpg

They are different species. I've grown both (or at least teh second one and one similar to the first one). No matter what you do to the second one, it grows like that. The leaves are more opposite than rosette. Not the most beautiful plant in the world, but I used it a lot for burns and cuts. Works great!!

There seems to be some confusion again with common names - Aloe vera is Aloe vera :-) Although that term is sometimes used to refer to ANY kind of aloe, there are not two species of true or common, aka medicinal aloe. There ARE many species of aloe....as many as 400 have been registered but true aloe, Aloe vera (formerly Aloe barbadensis), is the one noted for medicinal purposes. There is some documentation that Aloe arborescens also has similar medicinal properties but as the species name suggests, this has a much more tree-like growth habit and develops a distinct stem or trunk.

The difference in growth habits between the two plants shown in the pics is simply due to age and maturity. Aloe vera will form a full rosette if given sufficient time and proper growing conditions. Check the Wiki photo linked below.

The smaller ones that appear to only grow laterally rather than in a round rosette of leaves are just young, immature plants (offsets or pups) and hampered from full development by lack of time and indoor growing conditions.

Here is a link that might be useful: {{gwi:225039}}