The kit gives you the flexibilty to scratch build a gun to suit your wants/needs. You buy a prebuilt VFC, CA, or whatever .. maybe you don't like it's accuracy or power, or maybe the stock mechbox likes to crack after a few thousand rounds... you end up paying more for upgrades. So in the long run are you really saving?
I guess it comes down to whether you have the ability/tools required to build a gun, and whether you're willing to spend the extra cash now vs. spending it later.
KA and Guarder kits are made by the same 3rd party, KA pricing is generally cheaper.
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