Someone on the forum was banging on about them being better. I did try a tankful on a return trip from north Wales having done the trip there on tesco diesel. Not any difference in consumption or performance, just cost more.
I know it was only an insensitive test, but if you're paying quite a bit more, the difference should be noticeable.
you wont see the benefit on an old engine or just the occasional tankful. it contains extra lubricants and cleaners that prevent diesel filters and pipes getting blocked.
cheaper though is to add some 2 stroke oil for extra lubrication and the occasional flush with forte etc before changing the filter cartridge