The cockpit dimensions are on the catalina website. Or email them.
The 250 is narrower than the 270 by a foot or so. However, the 250 makes great use of space. Fantastically spacious interior for a 25 footer. Although you give up side decks.
The cockpits are similar in their crew capacity, and both have integrated stern seats. The 250 might feel a little more cramped with the narrower beam. The 270 gives up some space for the wheel, whereas you can lift the 250 tiller out of the way.
Both have walk-through transoms, but only the 270 had a swim step.
The 250 will be considerably less expensive to purchase, depending on year and equipment.
Also there are many advantages to an outboard for lake sailing.
Get the keel or wing keel version, not water ballast.
The 250 would be an outstanding lake sailor. Stunningly easy to sail, fast even in light air, and peerless accommodations in the size.
You have to remember that the 250 is about 2,000 lbs lighter than the 270, and combined with the narrower beam she will be noticeably tender.
She'll heel heavily in just moderate wind, and buck like a bronco in associated chop. A fair weather ocean sailor, but more than adequate for safe and comfortable lake sailing.
For a boat very much like the 270, but available in either diesel or outboard, plus less purchase cost, and faster than both the others, you might look at the Capri 26.