what makes euro hair better? or the preference? is this even the case?

Its not better. Its just more likely to be compatible with the hair of Europeans.
Some westerners find some Indian & Asian hair too coarse or too strong to blend in with their own hair.
Its more expensive because the individuals are paid for their hair as opposed to Indian hair which is primarily donated by Indian women.
Personally I have found very little discernible difference between Indian Remy hair and European hair and therefore not worth the added expense.

It all depends on where the European hair is sourced really as good quality Remi European hair can last considerably longer before it starts to show any oxidation etc..
Again Hersute quite rightly points out that that a lot of it is down to the hair texture.
I would tend to think that it is a far better option for full wigs with good hair length(popular for women) rather than toupees for guys but everyone has their own preference.
On a side note beware of vendors advertising European hair when it is just Asian hair that has been over processed to mimick the European texture.