I have mixed emotions about both. And as mclina said, there is a lot to be said about building the plane from a kit, and as Stickbuilder said too, but I think he is more of a stick builder (as his moniker states) meaning he buys balsa, buys the plans, then cuts the wood according to the plan, and builds accordingly. Now that's really building, and I've never tried that part, and don't think I have the time, talent, nor the patients for that kind of build.
But kits come in all sizes and difficulty levels. Most modern ones come with laser cut parts which makes that part a snap.
I put my first trainer together, it was a kit. It was fun to put together, but I had the time. When I discovered ARF's, I found that I could assemble (note I didn't say build..) them in a few nights, and be flying by that weekend. It's all a matter of what you want and how much time you can devote to it. Don't cut your time short, allow plenty of time for either an ARF or a KIT. And, if you want to scratch build, as Stickbuilder does.. well, add a little talent to that mix..
CGr.