Agreed with the others who said this: those are the same (or damn close!) design as the PPE's, which are ******* awesome. They picked a good design to, er, mimic...
The claimed gain is the same too... but where are their dynos?
The only ways I could see the original PPE design improved on would be (1) Make out of titanium or some other uber-pricey and light metal and (2) experiment with the design further to minimize the slight low end torque dip while maintaining all the gains up top (very likely impossible without some sort of variable runner design).
As to TP's vs. LTH: Here is a(n imperfect) comparison between my 2010 370Z with resonated TP's and Nismo weldina (Y-pipe version) vs. my 2011 370Z with PPE LTH + Nismo take off (H-pipe version). Both runs are under nearly identical ambient conditions and both have K&N panel filters plus the smooth tubes and a tune.
Because these are technically two different vehicles (although, of course, same engine model and on the same exact dyno...), these results should be interpreted with caution -- but I think are informative, nonetheless.
I think we can tentatively conclude that the PPE LTH + Nismo H-pipe set up is far superior up top (a whopping 13 or more whp), but a bit inferior down low (about 5 whp lost in a fairly narrow area).