lets say you have one product with 90 calories and all 90 calories are from fat, but then you have another product with 120 calories and only 75 calories from fat. Which one should I choose? I know this seems trivial but lets say this is a regular diet (hypothetically speaking of course).

Without knowing anything else, I'd go with the least processed/most natural choice.

Yeah, good point

Not all fats are created equal so keep an eye out for the processed hydrogenated fats

I'd look at fat consumption from a daily consumption of caloires point of view.

Just make sure that at the end of the day, when you look at your daily overall intake of caloires, fats comprise about 25%+/- of that total daily overall intake of caloires. And of that, that saturated fats don't exceed 7% ( per the AHA ) of that total daily overall intake of caloires. Remember most nuts are about 75% fat, but they contain mostly " good fats " and are a heathy snack option - even though they are very high in fat.

Now if you are asking if simply consuming fat makes you fat, the answer is no. You end up adding fat to your body because of consuming excess calories ( in excess of what your body needs each day ). So, excess calories from carbs, protien or fat may be stored as fat. Again, it's excess calories that make you gain fat.