I agree with all the above. It must be remembered that, ink jet or laser, the decal might look great when printed, but you will
not get the density of colour you'd expect to see from a commercially produced, litho or screen printed decal, once the decal is transferred to the model. Also, as Andy pointed out, ink jet-produced decals, in particular, are not particularly stable, and the printed image can very easily be degraded by excessive handling, even when sealed with a good quality acrylic varnish.
However, the density and stability of laser-printed decals tends to be slightly better.
Clear and white decal papers are available for both types of printer, and each will
not work in the other. There is also a 'press fix' type of decal paper available, which, in theory, could produce better density, but, of course, has slight limitations in actual use, as the decal must be placed accurately before 'pressing' into place.
All of these materials are best purchased from a specialist paper supplier, where the price per sheet, or per bulk pack in particular, will be
considerably less than the same material through a modelling outlet, particularly those products with a modelling brand name. I use a company in the UK, who will ship overseas, although there are sure to be equivalent companies worldwide.
If you wish to check on prices and avilability (in UK currency), go to
craftycomputerpapers.co.uk
Hope this helps.