I am not familiar with the Luci, but I've seen a lot of references to the Blu in a negative light. I've not heard anything negative really about the 510s -- some say they like others better, but I've not heard anything negative.
Well, actually... the only negative thing I've heard is battery life, which is solved if you get the PCC (the Blu comes with one, but again... have heard lots of yucky stories about the Blu).
Cignot has a great deal on the black and white colored 510s -- $35 for the starter kit. They also have a $65 starter kit that includes the PCC -- only $5 more than the Blu.
MyFreedomSmokes, with their 40% off coupon (code "smoke), might be a just slightly better deal than Cignot if you want the PCC and the starter kit together -- $41.97 for the starter kit, $19.17 for the PCC, so that's about $62 instead of $65. They also have the copper colored starter kits.
There are a few other websites if you want the other colors, but they are a bit more pricy.
I ordered my juice sampler from MyFreedomSmoke -- got a sampler of 6 10ml containers for $30, and they have 60ml containers for $26 when I find the flavor I like the best. But if you are wanting the Ecopure juice (the one that is VG and ethyl maltol and nicotine and flavor only, but doesn't come in a lot of flavors although you can add your own flavoring to their Fresh I think) Cignot is one of the few distributors of it in the US -- a 20ml bottle is $20. I've heard their English Toffee is good, and I will be trying it in the future.
I believe all cartridges for the 510s are refillable. I don't know about for the Blu.