Well my advice would be this...
If you can afford a mod like the SD, Provape, or any of the like, go for those.
Reason:
1. Most mods have exchangeable caps so you can use any atty, most include an adaption for 510 stuff... but then you can use 901, 801, so on and so forth...
2. Mods have replaceable batteries... they go dead you are not totally up that river with no paddle... you simply replace with a new battery.
3. Quality... Most mods are made from significantly higher grade materials, and often carry a much longer warranty then your assembly line high cost oneoff's
I for one looked at the SD and the PV1... I decided to get the PV1 with all the accessories, and when their high voltage caps come out, ill get those too.
I had 4 of 5 eGo batteries go bad on me, I do have a warranty, and they were replaced, but I would have rather been able to order a replacement battery for around 10 bucks and have it fast to replace the defective battery, and still be able to use my PV vs. ship the cascading failure model back and wait for the replacement to come in... which was a while... Stock/availability you know the drill.
In the end it is your call based on cost and all that, but if you were looking at a stock vs. a mod, I would say go mod all the way!
And happy vaping.