I like the look (and affordability) of the short M4 GP, even if it is as common as grass. That can on yours looks very good too. I don't think I've seen one with that stainless shield before. One thing about the M4 is there's no bracket bolt to help secure it and it depends on the pipe clamp to hold it on.
Like @JCW mentioned, I’ve had good Experiences with Leo Vince exhausts. I have also had Scorpion and now I’m about to fit an Akrapovic to the bike.
Go with a reputable brand that you like the look of and that has a removable baffle. No lose scenario.