I have owned and used both.
GPS
- Better for knowing exact carry distance for hazards, front & back of green etc. Laser is difficult to use in this matter
- Better for knowing distances for blind shots, doglegs (carrying the corner, distance for through the fairway)
- Probably better for playing new courses (provides more indepth info at a glance)
Laser
- Great for practice. Can place targets at specific distances (60, 70, 80 yards etc). Do this all the time to work on short game
- In my experience easier/simpler to use (no downloads). New lasers are much better at target acquistion than early models.
- Always know the exact distance to the flag
In the end, I kept my laser (Leupold, non slope measuring model so legal for tourney use). The big seller for me was the usefulness of it in practice. I also find that many of my playing partners, while they own a GPS, often get me to just laser the flag for them if we are standing beside each other (i.e. Par 3s) and rarely pull out their GPS, especially on courses they are familiar with.
Jay