The LG/Goldstar CD-i players originally came with their own CD-i thumbstick. While you had to buy Philips CD-i accessories if you wanted to use a mouse, trackerball or gun with your LG CD-i player, LG actually did design their own thumbstick, as you can see above. The same design was provided with the DVS and Knowlogy CD-i players, as these were just licensed LG models. CD-i member Retrostuff recently opened up both this LG thumbstick as well as the Philips thumbstick and some interesting differences came up.
This picture above is courtesy of Retrostuff. At the top you see the Philips thumbstick and its circuitboard of the thumb-pad. Below the LG version. The 'stripes' of the Philips circuitboard are used to provide the pressure sensitive responses: The harder you press, the better conductivity the tracks will have, resulting in a faster movement of the cursor. The LG version however just have a few points. If you press to the right, there is one point that is touched, and the cursor goes right.
The whole PCB is different, LG probably made an independent design. How do they compare in length? The LG/DVS version also only has one IR LED, while I see the Philips thumbstick has two. Does it make it easier to use the Philips thumbstick, because you have to point less accurately to the IR receiver? Another interesting aspect: The LG thumbsticks I've seen have 9 buttons. According to the inside, the design was made as if 12 buttons were possible. They either used a standard design which was also used in other products, but maybe there are also more versions of the LG stick, just as we've seen different versions of the Philips thumbstick with a different amount of buttons!
Both thumbsticks do not work according to the same IR protocol, which means they are in principle not interchangeable: You cannot use the LG thumbstick (RC5) on a Philips CD-i player that supports the RC6 protocol. Retrostuff adds on this: "The DVS controller is not compatible with [all] Philips CD-i players (RC5/RC6). While is not pressure sensitive, the cursor moves faster, the longer you press and hold the thumbpad in any direction. You can go very fast in circles, as long as you don't let go of the thumbpad. It doesn't get as fast as the RC6 Commander though. As long as you point the remote control towards the DVS player, it doesn't have any problems picking up the signal. The angle doesn't matter. The RC6 Commander however, is much stronger and even operates through reflection, i.e. you can point it to the floor, ceiling or behind you. Buttons that are not used/covered/cut out can be found in many remote controls."
[Thanks, Retrostuff]