I use the fleet regent and I can say that the only significant differences are the turn rate (which is minor) and the tac ens slot being on the regent instead of the eng ens.
Fleet Regent itself has the same hull and similar stats as the Fleet Excel. The Regent I own is the C-Store version and I found, personally, a noticeable difference to the Fleet Excel... it was wanting.
"The world ain't all sunshine and rainbows. It's a very mean and nasty place and I don't care how tough you are it will beat you to your knees and keep you there permanently if you let it. You, me, or nobody is gonna hit as hard as life. But it ain't about how hard ya hit. It's about how hard you can get hit and keep moving forward." - Rocky Balboa (2006)