Logic does sound worse than other DAW's when you get to the limits of your machine, because Apple changed it so that it ignores a certain number of dropped samples before throwing up an error. I'd imagine that you're not at that point though.
You're not the only person to make this observation. A lot of people have found that moving from Logic to Pro Tools sounds better. Although despite that it seems extremely difficult to demonstrate any difference. I wouldn't be surprised if this is something to do with the screen layout or colours affecting our perception. Colour and sound are closely linked and I wonder if something like that is going on.