I've done both, and had a great time with it. Right now, I'm enjoying a 1248 Fourth Imperium campaign. Who knows what the next one may hold?
If you go ATU, start small. It helps.
If you go OTU, take what you like and don't get bogged down with trying to keep it all accurate to the written word. For a home game, canon should be an aid, not a limit. (The opposite is true in writing for Traveller publications, of course.)
Best of luck, my friend, and let us know if you need any help,
Flynn
BTW, I recommend Galactic. It's reliable and it works. I haven't played with Universe yet, of course, so that might change, but money's tight right now, so that'll have to wait.