I have looked at the 34 and 36 Catalina's quite a bit. The 34 really lacks storage, very small galley, has a smaller salon but the berths are awesome and would say best in class.. The cockpits are identical between the two and just about a foot of difference in length. If day sailing or weekending is your goal, the 34 would be perfect.
The galley, salon and storage of the Catalina 36 is awesome. If it had a large cockpit lazarête it would be just about perfect. The rear berth can be tight for some. And lastly the head forward rather than by the companion way is an issue to some. For extended cruising, the 36 is hard to beat.
The versions with the walk through transom are much nicer with the MKII's adding a really nice cockpit and some more space below - it's significant
. I am not a fan of 36 mki due to the aft berth. Others would disagree.
The Pearson is a much more "dated" design. What that means depends on your taste.