Linear scale is very un-life'y, meaning that it rarely occurs in real life, therefore applying it to games is not always a good idea.
Logarythmic scale much better because it shows that on the high levels you have to put much effort for little reward, but on that level that reward is worth it. A proffesional athlete has to put a lot of effort (practice, diet, perhaps equipment) to get their time by few miliseconds faster. Also at the beginning you learn/progress very fast with very little effort. It may give so nice numbers as now 1k, 2k, 3k, etc. but if we discuss this, I'd recommend some formula based on logarythm.
For example purpose, imagine
x = effort put into the game (measured in hours of gameplay, I guess)
y = progress (here measured in lvl/skill gained)