This is an age old question that arises periodically.
In short remi hair is hair that has not been chemically treated to remove the cuticle.
The reason most hair is chemically stripped of its cuticle is to prevent tangling.
Remi hair is more expensive as it takes longer to tie as they have to align all the hair cuticles in the same direction to prevent tangling.
European hair is more scarce so is more expensive and that coupled with the hair being remi makes it even more expensive!
Indian hair is closer to European hair in texture but is usually chemically treated for not only ease of ventilation but to match European texture.
Chinese hair is basically fatter in diameter,actually more rounded, so to achieve the European texture it is even further chemically treated.
I have noticed that the quality of Indian hair is far better now than maybe say 10 years ago.
I put this down to a change in chemical treatments that they now use which maybe kinder to the hair?
To be perectly honest the Indian hair on offer now matches European hair very closely.
Obviously if any hair type is remi it will last longer quality wise because it hasn't been through the rigours of the chemical treatments.
My only advice to anyone is be very careful of companies offering European remi hair as quite often it is not,and unless you are very much clued up on hair types, you will get duped and be paying over the odds for what is basically Indian hair that has been treated to mimic European hair.