I have the Dreadnought. I'm not sure what the hull rating is on the Excelsior Refit, but the Dreadnought is 49,000 starting out. It can take a beating. You won't gain any extra weapon slots except for the spinal lance. It's really only good for hitting large objects, like Borg cubes and stations.The turn rate on the Excelsior is better then the Dreadnought. I don't remember what the console configuration is on the Excelsior Refit, but the Dreadnought has 2 science, 3 tactical and 4 engineering. I would keep the refit myself, unless you really like how the Dreadnought looks, like I do. I do not have the Odyssey, so I can't comment on it.
Absolutely stay away from the Drednaught. It isn't worth it.
If you're a tac and determined to fly a cruiser, you want either the Excelsior or the Galor. Both are capable tac ships. The Assault Cruiser can also work for some specialized builds. Stay away from any Galaxies, or the Star Cruiser and Odyssey starwhales. Leave those to the healbots.