It's always going to be down to personal preference in the end. Lots of choices usually revolving around style (slash cut, straight cut, rolled tips, burnt colour tips etc etc) and the material type (stainless steel, titanium, carbon fibre etc etc).
Aren't those welded on though on your backbox?
I know the Ark & Invidia tips are removable/adjustable but didn't think the Cobra ones were that's all.
If it's bolted on as you say then can you not re-tighten the bolt to stop the rattle or do you fancy changing the tips anyway?