I do agree P&T have more connection which is their only artistic edge and they have a better triple twist which is their only technical edge. That is it. S&S have stronger throws, much stronger lifts, stronger jumps, stronger in all other elements, better choreography, much better basic skating as you said, superior lines, better unision, much more polish (combining the two partners). The Germans by far outclass Pang & Tong overall in both the technical and presentation side of things if both are at their best.
As for the Zhangs back when they were at their best from 2005-2009 they were regularly beating Pang & Tong, and often by huge margins. Sometimes both pairs would skate cleanly in the short and the Zhangs would be 7 points ahead. And at an event like the 06 Olympics the Zhangs had a disaester and still won silver where a clean Pang & Tong settled for 4th place. At their best the Zhangs are technically far superior to Pang & Tong.
As for Petrova & Tikhonov, except for the 2006 Worlds (which many thought was a ripoff) a clean or reasonably good Petrova & Tikhonov always beat Pang & Tong. Pang & Tong only came out ahead when P&T had problems. If both teams had mistakes or both were clean Petrova & Tikhonov always won. Petrova & Tikhonov have a gold, silver, 2 bronzes, 2 4ths, at Worlds, and have won the European title twice. I think it is wrong to say they were never on par with the top teams, atleast they were certainly no less so than Pang & Tong. If you want to imply Petrova & Tikhonov were a 2nd tier sort of team, Pang & Tong must be too then. Nobody ever considered Pang & Tong to have a prayer of winning the Oly Gold the way teams like S&S, Z&S, S&Z, S&P, B&S, T&M were all atleast considered for a possible Olympic title once or more this decade, and most years they arent even considered threats to win Worlds (basically almost no years other than the 2 they won, and actually their 06 win was pretty much a shock at that) so it is not like they were ever considered one of the big guns anymore than Russian P&T.
Remember the Zhangs and Petrova & Tikhonov have both beaten both Shen & Zhou and Totmianina & Marinin, two teams Pang & Tong were never once able to beat even when they had major errors. That is another indication those 2 teams at their best are better than them, as they were more a threat to the very best teams. Heck Petrova & Tikhonov in their World Championship year beat Sale & Pelletier (who were already a big threat) 3 times in a row, something Pang & Tong would never have been capable of. And atleast they dominated most of their World Championship season, not winning Worlds by default since the reigning Oly winners both times (T&M in 06, S&Z in 2010), as I said two teams that P&T have never beaten before, skipped out.
I actually think Pang & Tong's biggest asset is their consistency. In that sense they are similar to Petrova & Tikhonov. They sometimes make mistakes but they rarely implode too badly or beat themselves, they can just be beaten by better pairs (which happens often). The sloppiness in her skating especialy can never be fixed, it just isnt in her.