The slip-fit is probably easier for a DIYer. Just make sure the stub for the tub spout is secured to the framing. If the tub spout piping is floating in mid air, secured only to the bottom of the tub/shower valve and nothing else, there'll always be a gap between the shower wall and the spout - you'll never get a nice tight fit.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!