We stepped up from a 22 ft day sailor to our Catalina 36 TR this year, and could not be happier. Before we bought, however, we chartered one in Florida. That charter was critically important to prove to us that we could live in the room, sleep in the berths, and handle the boat ourselves. Catalinas are common in the second-tier charter trade, so you can easily find one if you don't mind travelling. As noted earlier, when length goes up, volume goes up in cubes, so a 36 is much roomier than a 30, but also more to handle and costlier. I think that you get used to the size of your boat, just like you do when you first buy a larger or smaller car. After the first year, it's just the right size of boat. As noted previously, the systems are largely the same as your 30, but a bit larger (35 hp engine vs. a 25 hp engine - it still needs fuel, oil, and maintenance the same). As everyone says, the "perfect" boat is a balance between comfort, performance, durability, etc. We wanted the nice interior space and a 34 was just a little cramped, but did not feel comfortable single-handing the 38 or 40. For cruising, I think that the majority of tasks should be able to be done with a single crew member.
As far as V-berths, I understand the 34, 36, and 38 all have the same dimensions up there. Our 36 V-berth is enormous -- so much so that you need custom sheets because it's longer than standard king-sized fitted sheets. It is set high for structural reasons, so shorter people may need a 12-inch step stool to get over the edge. The extra two feet from 34 to 36 goes into the saloon and head. The 34 head is too small for me to change my mind in, much less my clothes! Everyone says that they use the aft cabin for guests, or mainly storage "the garage" -- I agree. That's where we keep our foulies, extra sails, water toys, etc. By the way, check out the Catalina 36 international association web page
https://www.catalina36.org/ Good luck, and let us know how it turns out.