I'm at the same school as UBTom, and yeah, both are just as hard if you are trying to get an A. But the experience probably differs from school to school.
I've had the exact same overall GPA during the two academic years and the one clinical year so far. That said, I tried VERY hard to get an A in the clinics and managed to get all my patients, requirements, practical exams, paperwork, scheduling all done and perfect. However, as wonderful as my dentistry & hand skills & patient care & personality is, I apparently suck at the very important skill of kissing serious instructor butt. B/c for us, what your teacher thinks of you is worth 60% of your clinical grade.
And I found it very hard to tell whether the teacher thinks you are fantastic or mediocre, but apparently, some of my classmates were much better at this game than me. I am a straight forward person - shady is not my style - so I was not about to play personality games with moody professors to figure out who was more likely to grade me higher in the clinics, while compromising what I was trying to learn and giving my patient the best care they deserved.
So if you can't already tell, I didn't get an A in the clinics. It felt like it was easier to get an A in the didactic courses. At least there if you didn't get an A or a B, you knew it was because you didn't study the right things or put enough time in. In clinic, you could never tell what mood the teacher was in with you or how they stacked you up against the other students (at least I never could) and couldn't control your grade as much, and that drove me nuts.
Bottom line: All four years are rough. There is no "easier" year, just different kinds of stresses in the different years.