I have all 3 and a lot of it comes to preference. I have the Hana v4d (dual battery) and my vapor shark is the rdna. My least favorite is the flask because of size and weight.
If you go with Hana, get the dual battery model. It's only a $10 different we envelope from the single battery. If you only want one battery, get the vapor shark. Also, take a loom at the sale Hana's, they are units that have scratches on them and are $30 cheaper. The scratches aren't that bad and they will text you photos before hand so you can see if it's bad.
Pros of Hana:
Aluminum box, multiple colors, dual battery, six month warranty, they're pretty, clicky Button's, fire button doesn't light up, Screen is on side, light weight, made in USA.
Cons: body scratches easy (I scratched mine by accidently rubbing a shirt that had jewels on it. Need a screwdriver to change battery, smaller screen, inside is not nice neat and clean (I can see the wires to battery contacts) Button's are not as comfortable to press, you'll have a difficult time using an atty larger than 22mm because of recessed 510 connector. Doesn't include battery
Pros of vapor shark
Smaller, durable finish, larger screen, comfortable buttons, easy to change battery, zip charging (only 1 1/2 hours), wireless charging, can use wider than 22mm atty, reverse battery warning, comes with battery, well built and very clean (no visible wires or glue) cheaper
Cons: screen on bottom, battery door can slide off, only one battery, heavier than Hana, fire button lights up, easy to accidently hit wattage up/down buttons if I had to buy another one, only comes in black. Only 4 month warranty
Personally, if I have to buy another, it would be the vapor shark.
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