Why is it any more of a toll in the SEC vs the Big Ten, for example? Is the Big Ten not a physical league? Fact is, the SEC has hung it's hat on defense and there are more Big Ten defenses in the top 25 of scoring than SEC defenses (and ironically enough one of those isn't a Michigan St team). I don't argue that the SEC doesn't have more talent overall top to bottom. But if that is in fact true, it doesn't make it any more of a gauntlet. If the SEC is A talent and the Big Ten is B talent, it's A vs A, and B vs B, not A vs B. So it's a wash when talking about getting through a schedule unscathed. I'm not going to entertain Iowa playing LSU's schedule, because that is fiction. If Iowa were playing LSU's schedule, they'd be benefiting from being in the South East and it's horde of talent. Last time I checked, Iowa hadn't drifted that far south and it was still populated by cornfields. And they all lived happily ever after. The end.
I will assume this isn't serious, but I will answer it just in case. No, the Big 10 isn't a physical league. In fact, it's a complete joke. It's either the worst, or next to the worst league of the Big 5(ACC may be worse, but it's debatable). Using the fact that they have more scoring defenses in the Top 25 is literally the most arbitrary thing you could use. I mean, outside of tOSU, who in the Big 10 has a decent offense? Michigan State score 27 against Oregon. Nebraska can't throw the ball. Wisconsin is worse through the air. It's just a horrid league.
As for the difference in the two, if you play in the SECw, you have runs like Ole Miss did this year with Bama, Auburn, LSU, TN, and Auburn over a 5 week span. In the big 10, those schools MIGHT play one game as tough as any of those. You get the weeks with Illinois, NW, Indiana, Purdue, Michigan, etc.....all terrible football teams. You just don't get those weekend breaks in the SEC(or the Pac 10, to be honest). The PAC isn't nearly as physical, but there are no gimmes out there.
In all seriousness, do you think there is one team in the Big 10 that wouldn't lose three games in the SEC? What about one Big 10 team that wouldn't lose 3 games in the PAC? I think you could probably argue they would lose 3 in the Big 12.
I do agree with you that you can't compare Iowa and LSU because the talent level is different. It certainly is, and that's exactly my point. Week in and week out the physicality here is just at a different level, because the athletes are better. Outside of the OL position, there isn't another spot on the field that the Big 10 compares to the SEC, and even that has become a wash.