You want the Hellblazer or the Hell-plane, whatever it's called. Able to rapid fire its secondary weapon, though ammo is short. It's my favorite of the new three - and looks great.
Plus, of course, you can't play online with anyone who uses the new planes or maps - so you may as well get them.
The new levels are no brainers - superior to the previous downloadable content, but I understand that they come from the single player game. Who cares? The Lost City rivals Sea Haven for my favorite map. Or Chicago. Heck, they're all good except that contrived Caverns map.
Don't know what else to write - It's free! Isn't that enough?