The V5.5 is probably better because it's the improved version of the V5. The V5.5 is the V5 Celebrity because you can try to get the Royal Family in it.
The difference is the V5 has different families (Mame, Meme, Voilet, Kuchipa, etc.) while the V5.5 has the Royal Family. The games are also different and the V5.5 has two more games than the V5. There are also new characters in the V5.5 that are not in the V5.
Other than that there are small differences like how all the tamas switch playing the games in the V5.5 while only the middle tama plays the games in the V5.
Hope I helped!