I am wondering if all ships have the same amount of space inside them or if some ships are actually bigger than others?
Some ships are bigger than others and the size differential between the smallest and largest ships is about 560 blocks.
The Human starter ship is has a relatively medium size at 3,752 blocks when fully upgraded.
The Novakid starter ship is the second largest ship at 3,760 blocks when fully upgraded.
In case you were wondering:
The biggest ship is the Floran starter ship which has 4,013 blocks when fully upgraded.
The smallest ship is the Hylotl starter ship which has 3,450 blocks when fully upgraded.