Final answer:
Upon jumping into a hole drilled through the Earth's center, you'd oscillate and become weightless at the core.
Choosing a galactic-mass black hole would reduce spaghettification, but in both cases, crossing the event horizon means falling into a region where escape is impossible and no information can escape back out.
Step-by-step explanation:
If you jump into a hole drilled through the center of Earth, you would experience a decrease in gravitational pull as you descend, and you would become weightless at the center because the Earth's mass would be pulling you equally in all directions.
Ignoring air resistance and assuming Earth is of uniform density, you would oscillate back and forth from one side of the Earth to the other, gradually slowing down due to air resistance until you come to rest at the center.
Regarding the second scenario involving black holes, the choice between a black hole with a mass equal to that of Jupiter and one with the mass of an entire galaxy would matter significantly when considering the experience at the event horizon.
You would want to choose the galactic-mass black hole because the tidal forces at the event horizon would be much less intense due to the larger size, prolonging the moment of spaghettification.
If you approach a small-mass black hole, the tidal forces between your feet and head would be so great that you would experience spaghettification before even crossing the event horizon.
As for the experience of an astronaut entering a black hole from the perspective of observers outside, they would see the astronaut slow down and fade away as they approach the event horizon.
However, the astronaut's subjective experience would be that time passes normally for them, and they would cross the event horizon without noticing anything unusual at that specific moment, ultimately reaching a point where escape is impossible and signals cannot be sent back.