Re: Headstock Decals - Vinyl or Waterslide
Unless it's a really high quality waterslide it will be quite visible that it's a water slide even under a finish. You can get stuff that is super fine almost like a skin membrane, which would not really be visible, but that's probably not what you're going to get with DIY ink jet printer stuff.
That said, the early Fenders used the former, very noticable that it's a waterslide. I've not done anything other than waterslide personally, a few years back I experimented with Fender logos on 2 Squier guitars, with both a cheap run of the mill waterslide and the more expensive stuff, the difference between the two is huge. The expensive one while looking better was extremely delicate though and requires quite some skill and care to apply.