I'm pretty new here but have some experience with the blu. I got one of the first

It's fantastic for travel, and yes it will charge a battery 5-6 times before the pack needs recharging. I love it because its easy to fit everything in my purse. It is (as far as I can tell) an 8084 which truly is the same size as a real cigarette. For me, it was the perfect introduction to vaping, because it appeased the fear of really giving something up. The batteries seem to last about 1/2 hour to an hour with heavy vaping, but they charge in about 45 minutes. The carts might equal about 2-4 regular cigs. The flavors are quite pleasant, but I don't think you can really appreciate them until you get some taste buds back. (Again, my own experience.)
All of that said, I also purchased a DES901b. It gives more vapor, and (I think) a better flavor for purchased e-liquids. (I've refilled both using TW juice and it just tastes better in the 901. My own home made juice tastes similar in both. I have no idea why... perhaps the glycerin...) The batteries and carts last significantly longer than the blu, (tho I've killed an atomizer already on the 901 and the blus are still perfect.) The atomizer on the 901 does seem to burn much hotter.
I've read/seen reviews on the 510 (Joye 510, Janty DuraC, Yeti, Titan) and I think that model will address the few issues that I have with the 901. I really like the idea of a sealed battery although I haven't had any problems with leaking on either model, and I like the concept of a manual switch. (I really want a super easy draw and some more consistent throat hit.) I've ordered one and am hoping it will arrive this week.
Overall for a person wanting to try this out... especially if they are still sort of unsure, the blu with its pack, plus charger, plus the 25 carts for the price AND it's similarity to an analog cigarette in FEEL, will go a long way to convincing someone that this really CAN be an option for them, before overwhelming them with 20 zillion batteries, atomizers, carts, bottles, juice, etc. Once were hooked tho, the sky is the limit, and smoking becomes not just an addiction and a habit, but a rather pleasant hobby with constant upgrades. The blu is fantastic for what it is... I do love mine and will continue to use it... but I'm glad there are some higher powered options
I'm really looking forward to hearing more about the Janty Stick... as I think that will be my next device
Hope this helps some!