If I were to choose from these two then I would go with Mechanical Orange because it's a design I've never seen before. The game is very easy to play, there is only one line for winning and you only have to hit 3 of them same simbols in order to get a win. Perfect gems is pretty good but I've seen this type of game before, they only added new simbols and new sounds.
It was my first time to play a slot game like BGaming's Mechanical Orange. The structure is different. The gameplay is very simple, yet the design is really quite a good sight to behold. Aesthetically, Merchanical Orange is top-tier.