It's not really easy to describe one as the best, because they are all different and meant for different vaping styles/user types.
I think the first one looks the best. The two tone design is really cool. But, it isn't adjustable as far as I can tell. It seems like an inexpensive option for a new vaper or someone looking to upgrade from a very, very basic starter kit or eGo to something more complex.
The last one is kind of on the same level as the first. As far as being something simpler for a new vaper, Or a first upgrade step. This one looks really uncomfortable to hold, but it adjusts, which is a better feature to have than the first one. It looks like they are priced with only $1 difference, which seems ok because they are both on the same level, but are 2 different ways to go, depending on what things are most important to the user.
As for #2, #3 and #4 These seem to be for a more experienced vaper, especially with the high output on the mod. If the customer was just looking for a tank or a mod, then options #3 and #4 give them that. If they were looking for both, obviously option #4.
If I were picking one for myself that best fit my current situation as a vaper, and had a choice between these five options as to which one I would buy now if money were not an object, I would pick #2, the 300w Wismec Reuleaux RX Gen3 with Gnome TC Kit.
If I were picking the best looking option, that would choose #1, the Smok Priv V8. But since it only has a fire button and no other options, I don't think it is functional enough for me at this point. When I was first vaping or a few weeks in, it would have been a good option.