42" plasma is the best for SD, and definitely the best overall for DSTV including HD PVR. Especially for sport. I also maintain it whips Series 5 LCD at HD and FHD content (I have a Series 4 plasma and Series 5 LCD); but those sold on FHD and resolution will go with the LCD's resolution instead of plasma's picture quality.
Just had two friends over the past few days for the first time (both LCD owners) and blew them away when I demo'd my 42" plasma on SD DSTV and HD DSTV.
The difference between HD and FHD mainly depends on the content, room set up and the person. The viewing distance for a full FHD experience on ±40" is 1.5m; 50" is 2m. Best to go and see for yourself in the store.
I can't imagine you'll be watching more than 10% FHD content. I'd say go with the new 43" Samsung plasma PS43D450. You also get 3D if you're sold on it

in the PS43D490 at about R7k.