Whether you build your own or just buy premade there's going to be a learning curve with building it and finding what works and doesn't for your tank and juices, and you'll have no option with the coil ID and ohms if you buy them premade(though technically you could remove wraps on a premade, you'll have no means to go the other way). Premade is nice, but for something you'll spend time learning anyway, wrapping some wire around a rod really isn't the hard part, but i'd certainly buy premade for complex coils(claptons and so on). As nice as the DIY kits are, chances are you'll have something already to hand to do the job for most of the tools they provide, the jig is the most vital part(though those aren't even necessary it makes things much easier) imho(and some appropriate wire clippers), nigh on everything else can be emulated with a cheap as chips implement from a local shop(or by something laying in your toolbox/drawer).