In terms of finished appearance, refinishing wins this comparison. While judging appearance is always a matter of personal preference, most people find that refinishing produces better results because the process maintains the exact contours of your current bathtub.
One exception is if the old tub is in particularly bad shape—rusted, cracked, scratched, or dented. Here, completely covering the old tub with a liner may produce better results. However, if you have a unique bathtub or one with a unique shape that you like, refinishing maintains the same lines, just with a new surface.
Bathtub liners slightly reduce the inner size of your bathtub, which may be a problem for users who like to use the tub to take baths.
Source: The Spruce