Run blocking tends to be easier, since you're responsible for taking out your guy, attacking the defender, especially in a man to man blocking scheme. Now, if you're undersized and / or underpowered, you may be in for a bad day if you have to take on those 300+ lb monsters at nose tackle or 3 technique DT, and have to get a lot lower.
On a passing play, you're more in a "stand your ground" mode, and are trying to delay the pass rusher. Offensive linemen tend to prefer being the one hitting the other guy.
But... It also depends on the scheme.
The offensive schemes that we've been using ever since 2005 all used zone blocking (Charlie Weis' Erhardt-Perkins offense, Brian Kelly / Tommy Rees' pro-style / spread hybrid), and it takes time for a unit to mesh together and be on the same page. It's one thing to understand the zone blocking assignments, but it's another thing to actually be able to make quick decisions on which defender to block once they're in your assigned zone.
It also comes down to being able to pass off the guy you're blocking, to another blocker, or to be the one receiving the defender being passed to you.
Once a bunch of guys work together, they learn what each other's real time strengths and weaknesses are, and can all adjust on the fly.
In the case of Saturday's performance, there were some blown assignments in the running game on multiple occasions, during the first half, especially on the left side. Knapp didn't adjust to the stunting a few times, while Pendleton flat-out chose to block the wrong defender a few times, most notably on the play where the nose tackle who was already double teamed. The 3 technique DT was left unblocked, and smothered the runner.
After halftime, the left side of the line looked significantly better, and I'd attribute this to Joe Rudolph making adjustments and doing some on the spot coaching. Knapp and Pendleton did a much better job of reading the zone and taking out the correct guy, while also doing a pretty good job of passing off defenders to the TE or blocking RB, both in the running and passing plays.
I'll definitely say this, that our linemen have flexible minds, and made adjustments properly, especially as the game dragged on into 4Q.