At its size, it'd beat anything - Full HD or not - for the quality of its picture processing. The best plasmas are still ahead of LCDs for fast motion rendering - kind of essential for gaming! - and with extra contrast and true blacks on offer, you'll see a lot more of the on-screen action, even if the Full HD screens may offer a tiny bit more detail (with Full HD content).
If I had the money for the Pioneer, i'd buy it over any other TV at that size - or about any other size, come to think of it. It's only bettered by the bigger Full HD Kuros.