My $.02:
1) If you are under ~525whp just save your $$ and run the OE pipe. At the ~+525whp ranges I'd only begin to consider. (NOTE: Based on LHD models, RHD is different conversation).
2) PSP Aluminum outlets seem to be very nice units, but can have some bead rolling issues due to some production limitations (seems to be more aesthetic and have no reports to cause any issues). Primary tubing a bit on the large size at 2" OD, but it is what it is. Ultimately the primary runs are very short so if it means the trade off in that merger excellence then I'll take it. Unfortunately no transitional adapters.
3) VRSF Aluminum outlets seem to be direct PSP ripoffs, thus are also very nice. Also unfortunately no transitional adapters.
4) VTT Aluminum outlets are not bad, but the merge has some room for improvement. Honestly I'm a fan of the tasteful 1.5" OD primary tubing, which is a reasonable match for the N54 style housings pushed hard (~1.5"-1.75" is ideal IMO). Sadly some significant shyster'esque marketing on the flow results against OEM Pipe. Also unfortunately no transitional adapters.
Rob