JR, there''s a lot of content wrapped up in Jeff''s and Jon''s replies but the reality of your circumstances - buying a 25'' sailboat - will probably present you with only one option: deck stepped mast. It would be a totally acceptable choice for you, assuming the boat was properly engineered.
I share the same preference Jeff does re: deck vs. keel stepped (altho'' I sail offshore with the alleged ''better'' keel-stepped mast) but, for a small boat which has simplicity as one of it''s key benefits, I would think a deck stepped mast would be far preferable: easily raised/lowered by you with some inexpensive
line, rings and tackle and no deck penetration to worry about re: weather when unstepped. Can''t imagine why you would want to change ''simple'' for more complicated (and most likely a bit more expensive).
Jack