Observation!
An inference is something you can’t directly see or feel, like in this case you might *infer* that Object A is made of a more durable material because it is heavier.
On the other hand, an observation is something you can directly see or understand. In this case, you felt that Object A was heavier and knew from feeling it that it was heavier.
In conclusion; an observation is something you can directly observe, while an inference is something you make when using logic to decide something about something.