Raising Toddlers - More Difficult Than Raising Grade School Kids?

I had a long discussion with my BFF today, regarding a tweet I posted yesterday; "Wow someone needs to teach that kid to listen...oh..that's MY kid and that teacher is me." Yesterday was one of those days where Mr. L decided to test all boundaries (And my patience) and disregard all direction I suggested and any instructions I gave. It was beyond frustrating because while I know that he understands me and can hear me and when willing, can follow my directions, there was no way for me to reason with him...he's 20 months old! I can't say to him "Look, you need to get off your bike and walk to the car because we have to go to the grocery store so Mommy can buy food for you to eat so you can eat dinner and not go hungry..."...trust me, I tried. Yesterday was a day that I felt defeated. Every corner was another conflict and another tantrum. My friend tells me "Welcome to age 2". Great.
But, in talking with my BFF, we had to ask the question "Is raising a toddler REALLY more difficult than raising a grade-school child, a preteen or a teenager like everyone tells us it will be?" While yes, the thought of raising a teenager is enough to make a mother stay up all night in a panic, the thought of raising a child between the ages of 5 and 12 seems like it will be so much more do-able than raising a 1 to 2 year old child. I'm not saying it's not difficult to raise a grade-school or preteen child, I am sure that it is, but I think it's not necessarily hardER, just a different kind of hard, no? In my mind, it all comes down to having the ability to reason with your child. Having a child, who can understand the basic concepts of right and wrong, unacceptable vs acceptable - I don't think my 20 month old is there yet. Maybe he is and I'm just not giving him the benefit of the doubt, but I am just so looking forward to the day where I can lay down some solid consequences to behavior and actually get results.
I'm sure I will look back on this post in 5 years as I'm pulling my hair out as my 6 year old is doing something so beyond disobedient I never thought it was possible, and laugh. But until then, I'm asking you - what do you think is more difficult - raising a toddler or raising a grade-school/preteen child?