You definitely have to factor in attack boosters, because they are a massive
boost to the orc. For instance:
Orc with 900 Convertion points is easily beaten by a Human with 400 convertion points less!
This is wrong; the 900 CP orc still is beating the 500 CP human at level 10.
900 CP = 11 conversions = 72 base attack * 1.3 attack bonus = 93 damage
500 CP = 5 conversions = 50 base attack * 1.8 attack bonus = 90 damage
The boosters are certainly a big variable for a level 1 comparison, but by a level 10 comparison it's a forgone conclusion that you have all three.
The toughest part is that any
conversion-heavy approach with these two races is going to put a lot of emphasis on complementary items to boost their performance, so you have a lot of factors to account for. I'll rarely send a serious orc run into a dungeon without a perseverence badge (small item +10% attack bonus), for instance. Then there's the consideration that the orc's stronger performance at lower levels will allow him to garner more bonus XP and actually out-level a comparable human.
These sort of graphs are useful, but there are some many potential factors to take into account that it really comes down to one very simple lesson: orcs are better early, humans are better late. Anything more really depends on what assets you have at your disposal.