I have the extension cap for the mini, so you're saying it's now the same length as a standard?! This thing is STILL small! I hope they come out with the longer extension cap for the minis. I contacted Provape.com support, and they said they'd pass it along to their designers. That way, we can use the really big batteries with the mini, with the option to downgrade when we want to stealth vape.
Even with the extension cap it's still around 1/4" shorter than the full size. There's side by side pics floating around somewhere here. I also thought I'd like to be able to use the 18650's when I first bought my mini. I can't say for sure I'd like it now. I really like how it's pocket friendly, doesn't fall out of my pocket "T's" and I'm getting around 6hrs of runtime out of the 18350's, I'm not going to complain about that after using a BB and getting maybe 3hrs out of a unit the same size.
For the OP, if you really like the Legacy mini, go with the Provari mini. I was looking at the Legacy myself, for some reason or another? But side by side there was less then 1/4" difference in the lengths of them, at least in the pics I saw. This allows you the use of batteries you have, in a form factor you like. Such as myself, I really liked the size of my BB and hated to go any bigger then that. The ProV is just a bit larger diameter, but the same length. I'm very pleased with the size, but, as I've stated before, I wish the button was closer to the top.
As for new or used, that's up to you. I was ready to pull the trigger on a used one one night, then I went to Provape and put the same package together, it was like $5 cheaper to buy the NEW one! So watch yourself on that one! I've seen a few of them go for a good price, but you better hover over the classifieds and be ready, most are gone in around five min! If you can find what you want for a good price used, go for it, I doubt anyone that owned one could really do much to harm it and most sellers are honest about the flaws in the add.