The only advantage I see in buying a preassembled kit is, you will have all the parts needed to build a firearm in one box. I did that on my first two builds, but on my Verner inspired squirrel rifle, I decided to buy the parts piecemeal as I needed/could afford them. PLus any parts I could make myself such as the side plate and or toe plate, so only need to buy sheet brass for those, which can be used to make many parts from. That and using spares from previous builds that weren't originally needed like extra screws, pin material bought, extra vent hole liner. It all helps in the long run and saves money. I've got probably $650 invested in total on the gun I'm building now. Many kits cost much more than that, and trust me, you're paying to have someone else put all those parts together in a box for you.