Five formats for a single-sheet handout. The decision is mostly about how it reaches people. Handed over one at a time, dropped through doors in thousands, or left behind after a meeting, because that sets the stock and finish more than the content does. Filter by distribution.

8.5″ × 11″ flat sheet, the default for events and promotion.

Your size, stock and fold, no standard format fits.

4″ × 6″ postcard scale: volume, mailing and door drops.

Cover weight, restrained finish. A leave-behind after a meeting.

Cut to a shape. It must not look like a flyer.
For volume distribution, text weight is right: most pieces are read once and the saving per thousand is where the budget does more good. The 4 x 6 format takes that further (less paper per piece, more per press sheet, and it mails unfolded) at the cost of carrying only one offer and one call to action. That constraint is usually a feature, since a door-drop flyer rarely achieves more than that regardless of size.
Anything handed over personally is judged differently. Cover weight and a restrained finish make the same size read as a document rather than as advertising, which is the whole point of a leave-behind. A shaped die cut is the most reliable way to not look like a flyer in a stack of them, though the die is a real cost on short runs. Print both sides in almost every case. The press pass is happening anyway, so the second surface is nearly free.