Hi Ben,
The FretFX product is first rate and can be easily removed with no damage to the guitar. However, once you apply it (about 10 minutes), you won't want to remove it. If your Ritter has a small peghead, you may only be able to mount the small battery box for the red LED's. The other color LED's take the bigger battery box. I have put FretFX LED's on 4 of my basses, and love them. They come with a 3 position switch: low power, off, high power. See the pics in this post. AAA batteries last a long time, too. The Fret Lord products look temporary, and a bit intrusive for playing. (Try tuning around the flashlight and fibre-optic cable!) They also look like they could be easily dislodged while playing, not a good visual during a solo?
Kris