[Wavytone]

Assuming you're limited to a 1.25" barrel the choice is determined by the size of the field stop. At 1500 mm fl the diameter of the moons image will be about 13mm across.

This suggests your 25mm is one that has a field stop about 15mm, such as an old Kellner. The largest field of view is determined by the field stop (ie the inside diameter of the barrel) - not focal length.

For example the Televue Panoptic 24mm and Explore scientific 24mm 68 degree eyepieces has a 27mm field stop - pretty much the maximum possible - yet much the same fl as your current eyepiece.

A televue 32 mm plossl also has a 27mm field stop - same field of view, less magnification.