Not to feed the fire or anything...
Speaking as someone who played soccer for 2 years, switched to football for a while, and then went back to soccer again, i have a pretty good idea of what's harder. Granted that my school is super crazy about football (we're like 17th in the nation, we could have been higher but we end up playing like our 5th string in most games since we always win by so much), i have to say that football is more intense. Yeah, yeah, soccer requires a bunch of endurance, finesse, and skill. It's hard to keep up at the end of the second half. Whoever said you can be the scrawniest kid on the field and be the best too is wrong, it's not like soccer isn't physical. If you're not strong you get pushed away/off the ball, simple as that. At my school though, the football players only get about a month and a half of off season. Winter weights are 3 hours 3 days a week. first half hour is warm up sprints, next hour or so is lifting, last hour or so is speed/agility. When spring football starts they run plays and shit on the off days. When summer starts they have practice every day from 7 in the morning til noon, and for a few weeks they go from 9 until 5. It's intense. Both sports are hard to compare, because they kind of require different types of endurance, but football is definitely the greater of two evils. Maybe it's just my school, i don't know.
Spark notes: Football is harder than soccer