Well, I think many of us have passed trough that dilema. It depends in many factors, being the first one personal preference. However, cost, design, brand, sound, bike usage, etc. may affect your decision.
After a lot of research I decided for a Titanium Remus Hypercone exhaust, and I got it based on the following factors:
1-I like the Termis since they're official Ducati stuff, but they're very expensive. So yeah, cost it is.
2-I like a cleaner look that shows better the rear wheel, so I looked at the Competition Werkes exhaust which is the smallest and relatively cheap, but I've seen some reliability issues and it points slightly upward. I plan to have some SW-Motech saddlebags and I don't want them to get burned by the exhaust, so I looked for another option with the exhaust pointing in a similar direction as the OEM exhaust
3-Akrapovic is a good brand and have a lot of experience in the automitive industry. Actually, they officially do some exhausts for Ducati's Panigale lineup. But, the exhuast is too long for my taste and goes against point 2
4-Remus is also a good brand with a lot automotive experience too, the price is similar to Akrapovic (and around half of the Termis) it comes with all the adaptors, DB killer and brackets (some brands require aditional link pipes or DB killer) and the audio clips I found on the web sounded very nice.
5-For other brands I checked (Arrow, Mivv, etc) either I didn't like the design or were not practical to import over here.
My impressions with the Remus:
-It sounds AWESOME, I didn't bother to test it with the DB killer so I cannot give you that feedback, but without it sounds great, a deeper growlat idle, and much more aggresive when putting gas on it. For my taste is not that loud but the DB killer is always an option.
-It's much more compact and lighter than the OEM, I didn't weighted it but I don't race my bike so it's not that important to me.
-It's easy to install, 2 bolts and some elbow grease.
-I feel the bike has a better response, but it might be my imagination (however I enjoy it even more with the new exhaust)
-I don't know how much power do I really get, but the bike already has enough for me.
-it sounds AWESOME, yes, it deserves an extra point.
Attached are before and after pics, I haven't had time or a nice day to take pictures of the complete bike but you'll get the idea.
Below are the links for the before and after sound tests, it's only at idle for now, I will upload a riding clip once I get proper wind noise cancellation.
In the end, it comes to your own preference, this just might help you on your research.