The caravela is smaller than the nemesis in 18350 mode but only by a mm or so.
The nemesis felt more durable and bombproof if you will, than my caravela does.
For example when I got a battery stuck inside my nemesis nothing would get it apart, we had it in the garage at work with the biggest eagle beaks and pressure vice we had, still couldn't get it apart, literally had to rip apart the switch and pry the bottom threads off to get into it. However if this had of happened in the caravela I know it wouldn't of taken much to get it apart to get the battery back.
I'm not sure what the voltage drop difference is but I remember seeing a member compare them both before with a few other mods, i think the difference was .1v in the nemesis' favour. Overall though for looks, i'd personally go for the caravela, out of all the clones i have and have had, private v2, udt v8, nemesis, turtleship, caravela and stingray the caravela is my second favourite due to how god damn smart it looks with a KFL+ on top, they sit together extremely well and with a k-nano kit using the cav in 18350, it's palm-tiny.
My favourites the stingray and the nemesis followed closely behind the caravel.