In all seriousness, LFR is more difficult than Normal, in my opinion. You have many more people that simply do not know fights, or do not care about mechanics, pulling extra mobs, and simply AFKing/alt-tabbing. This is much rarer of a case in normal modes, the only saving grace being that in LFR whenever there is a wipe people leave (or are kicked) and are immediately replaced via the queuing system. While normal mode is harder, groups are significantly more organized, generally have voice utility, have less people tabbing/AFK, and care substantially more about participating in the fights. Therefore, in my opinion, LFR is significantly more stressful and frustrating than normal, even if it is only slightly more difficult.