The Kadet Kit is one of the most accurate conversion kits I've seen -- far more accurate than the Ceiner kits that are made under that name or under the Kimber or Wilson name (or for Berettas, etc.) But, it isn't as accurate as a Marvel kit. Few guns are.
I've shot a Marvel, and I have a Kadet... (My Kadet kit mounted on my 85 Combat was as accurate as my stainless Ruger Target Competition with a long Bull Barrel. I traded the Ruger for a Witness .45 Sport Long Slide and
kept the Kadet.)
But I use the Kadet as a training aid and an inexpensive way to shoot my 75B Compact and 85 Combat. I don't use it for bullseye competition -- which, arguably, is what the Marvel was designed to do best. The Kadet Kit works with SA or DA/SA guns. It works with the decocker models.
Chances are, however, YOU won't be able to shoot well enough to take advantage of the Marvel kits accuracy... (I sure as crap can't.)
Do you already have a CZ-75 or a 1911? If so, which do you want to shoot more? Which do you WANT to shoot more. That will probably make the decision for you.