Why do different pokemon give different experience at the same level?

Question

for example, a lv17 Roselia may give 200 exp, then the same level wooper may give 150 .
This is under the assumption that I'm using no items, the same pokemon and at the same level? Why is this?
Which pokemon would give off the most experience?

Answer 1

Because Wooper and Roselia have different Base EXP stats:
Wooper has a base 50.
Roselia has a base 152.

AUDINO will give the most: Base 390.