Hiya Simon,
I was wondering same thing very recently having read and read exhausts on this forum I went for the MTC stainless Oval and can personally recommend them. Cracking noise with baffle in but the last couple of rides I have had the baffles out even better in my opinion.

Also rang insurance to let them know informed them they were cosmetic and answer that will be no cost I will stick a note on your file and sort next time you re-new.

Cant comment on the 2 - 1 others will probably have information on them but for me mine look good, sound good, value for money and lifetime guarantee.

that is M.H.O. for what its worth,
Steve