You've hit on one of the most recurring topics in the forum: best exhaust for the 9xx. While there are many strong opinions, I don't think there's a conclusive best brand. I read a lots of posts and asked a bunch of questions last year when making the decision myself. The only uniform agreement I found was that the stock cans blow and almost any aftermarket slip-on is a substantial upgrade in terms of heat, weight and sound. I don't think any slip-ons offer major performance enhancement by themselves.
I'm not critical of anyone who goes with Akra or Wings. I looked at them and think they are great pipes. If someone wants to pay for the bling, god bless. I just didn't think they were any better than most cheaper brands on the measures that were important to me. I specifically didn't want the Ti or carbon b/c I value durability much more that literally one pound difference in weight. I ended up choosing FMFs b/c they dominate the dirtbike exhaust market and are engineered and built to take extraordinary punishment. KTM uses them on its higher-end dirtbikes. IMHO, the build quality is superior. Not sure where you got the concern re rivets or welds failing.
I also like the clean (and slightly smaller) look of the FMFs:
I'm not a label buyer. My only advice is to figure out what's important to you then find a bunch of different pipes to actually see in person to make your own call on issues of weight, sound, heat, looks, etc.