Jay, if you haven't already, you might try a search on yachtworld -- single engine, gas, 26-30' -- and see what comes up.
Yes, it's a choice issue. Yes, pros/cons. Yes, new 7- and 8-liter gas blocks not widely available. Yes, space for twins in smallish cruiser is an issue. That market segment is also slightly diluted, with inboards, stern drives, and gas outboards. And so forth...
Also, I suspect more buyers these days tend to lean toward twins because they're after the handling advantages during docking
. (Although I've not found it particularly threatening to dock
the single-diesel we had before.)
"Lobster boats" and the like come to mind, but I'd suspect many of those would be single diesel