What is the best kind of progression?

All the games have their own complex formulas for progression but it boils down to 4 kinds:

*Logarithmic: When you start getting levels/money/etc very fast and then it slows down.

*Linear: When the progress never goes faster or slower, it stays the same way.

*Exponential: When the game starts slow but then it goes faster and faster.

*Combined/stratificated: When the game changes from any one of the last ones to another one, EG: exponential>linear.

What would be the best one to keep players invested and why would it be? i find that the combined one is the best because it makes everything shift gears after a certain amount of time/levels.