Welcome to the forum, where a lot of nice helpful sailors and a few old cranks hang out.
Firstly, having owned and sailed an
Alberg design for ten years I find them very
seaworthy. A friend and several others as well have sailed
Alberg 30’s around the world. They have generally never been accused of being roomy, but that means less rattle around room in a seaway. The
Ericson 35 is very similar to an Alberg-designed
Pearson 35 ( not the Bill Shaw design) which may be more available. Of the two you mention I would opt for the Ericson as being slightly more roomy, but if you’re planning to singlehand, just remember that more size means more challenge for the solo sailor, assuming that
electric winches, bow thruster, etc. are absent.
Having sailed a yawl now for 27 years, I wouldn’t
trade it for any other rig. But we don’t always set the mizzen. I have sailed on ketches, and find the ketch’s mizzen annoying to constantly look around while at the
helm. But like many other things, I am sure one can eventually adjust to it.