Fiat - we seem to be going round and round...there isn't a logical reason for the plants to be called how and what they are...Cacti are almost exclusively from the americas...Aloes are almost all from africa and middle east. I find Wikipedia really helpful as a quick reading source. One thing it says specifically about aloe is that many have naturalized to other parts of the world (the americas and the mediterranean, but their origins are from africa)
For me the classifications seem somewhat random, because they're often based on botanists or field scientists personal ideas of what looked like what and therefor classing things together. This is being corrected via genetic tests for distinguishing which family they should be included in.
Hope that helps. Personally for me I go by if its smooth its probably a succulent if its spikey (not spines like on an aloe - I'm considering that smooth) but spikey like OUCH!! that's a cactus
To clarify though - as Tarev and Tiffany (I think) said - for me its all about what info is this information giving me about the plants needs...for example I'm just getting into aloes - now looking on Wikipedia I see that they are from southern africa, that tells me that they need warmth, and are probably less able to take cold than cacti or other plants from colder areas. (it happens that I chose several aloe though that are more cold hardy to try some outside year round for me here in Seattle) But the point in distinguishing between cacti or succulent is really just to give you another clue about needs. Same with knowing the USDA zones tolerances of a plant, that helps me often! Hope this helps
