If you require the words themselves, as opposed to the numerals, I would be much more in favor of "point two five," than of "point twenty-five." From a stylistic perspective, it's more concise, and from a mathematical perspective, "point two five" sounds more correct. After all, .25 implies nothing like 25 because the 2 is in the tenths place, not the tens. Twenty-five just sounds wrong. Now, "twenty-five hundredths," while correct, should immediately be dismissed as too unwieldy in all but the most formal writing.