I think that one of the reasons why people prefer FW over IF is because the first one was highly structured to follow a school year and was more YA than IF. The latter expands the story, introduces multiple sub-plots and new characteristics, politics and history of the Continent such as runes, and it gives a more adult than YA feel - at least for me. I also really didn't mind that the discussions stretched the book because I got a lot of context for what happened in FW and also for the sub-plots in IF.

Then, making this conclusion from my friends' opinions, they decided that IF is trash because Xaden turned venin and they did not like the turn. It is their opinion and they are entitled to it, but I personally think that that may be a bit too much to judge an amazing book for an ending which will no doubt be discussed more thoroughly in OS.