Do colleges consider a 34 as much more highly than a 32/33? Especially since a 33 = ~2190 on the old SAT and 34 = ~2260 SAT. I keep scoring in the 32-34 range on practice tests, but I feel that the pressure of the actual test will make me score a 32 or 33, rather than a 34. Will that make a big difference?
Yes, a 34 composite score is considered better than a 32 composite score, although whether or not that makes a difference in your application depends on some extent on the colleges to which you're applying and your overall GPA. As a general rule of thumb, the more competitive the school and the lower your current GPA, the more of an impact your ACT score will have.
The reason why a 34 is better than a 32 comes down to how many students are able to achieve each score. As we discuss in this article, it's not surprising for your ACT score to vary as much as 3 points between different test administrations - maybe you did better with timing on one test, or ran into a few unlucky guesses on the other. However, nearly twice as many students get a 32 as get a 34 on the ACT - in the graduating class of 2015, 28,619 students got a 32, while only 15,829 got a 34. The percentile difference between these two scores may not seem that large (a 32 on the ACT is better than or equal to 97% of students, while a 34 is better than or equal to 99% of students), but when other factors like GPA and competitiveness of the school come into play, a seemingly insignificant different in scores can actually have a huge effect.
If you're applying to a school where you're already matching or exceeding 75% of students, then a 32 is a fine score. But in a vacuum, and especially if your GPA is on the low side, a 34 is better for college admissions.