I had both at one time - a satin A25 and a gloss A50. Sold the A25 after bringing it over to a friend's house and playing it against a Seagull (lower end satin finish) and feeling like they were very similar tonally. That A25 was a good guitar, just not Guild-good to my ear. I had played a gloss A25 years ago that I liked better than the satin one I ended up with, so maybe it was just the satin finish I didn't get along with...
The A50 I've hung onto because it's so distinctive in it's tone. Dry, woody, balanced, with some power too. Not much bass - the body of the A25/A50s look like an OM with the bottom of the instrument flattened. It's a good guitar for single string stuff up the neck as well as finger style playing, and it records pretty sweetly too.