Pros: Fit, Fit, Fit
If you truly want a custom fit Zipfits are the only way to go. Having foam liners allow every nook and cranny to be filled with no cutting and taping like you would with a stock liner. Stock liners (higher end only) can give you maybe 80 days of solid service and then you find yourself buckling tighter which then crushes your foot. With worn out liners what to do with a perfectly good shell? That's where Zipfits come in as the amount of days that you can ski before they breakdown is in the range of 300. One caveat, buy and have them fitted by an experienced boot fitter.