Yes, they have all built in ABL, but there are differences in max full screen brightness..
As you know a full white picture draws the maximum of power.. And Full HD Model need much more power to achieve the same brightness because of more pixels. The PX60U HD Ready 42inch draws max. 390Watt.. So it is HD Ready and power draw is high = high full screen brightness
If you are searching for a similar super bright Plasma tv, the PX8 U HD Ready Model also has around 100nits fullscreen..
What other Plasma TVs do you own?
2013 Panasonic TX-P42STW60 PDP
2013 Panasonic TX-P42X60E PDP