I've spent time with the Sony 46" CX520. Not impressed at all. Screen is not bright and the menu's aren't as nice as Samsung. The 46" CX520 is on the same level as all other entry level FHD LCDs.
To add, virtually all Sony LCD TVs are branded BRAVIA these days - means nothing IMO. All brands have their own engines, BRAVIA jsut sells the most because it sounds the best.
Also remember Samsung and Sony have a joint venture in LCD panel production, so they tend to use the same panels.
Furthermore, LED is marketing gimmick and offers same picture quality as LCD, albeit slightly brighter. There are very few true LED TVs, the ones you know are LED back-lit (edge-lit) LCD. Only the back-light differs (LED vs CCFL), the light still passes through the same LCD matrix. Not ever worth the 10% premium.
The real question is, what do you need the TV for?
If SD/sport/motion is a priority then Samsung 51" FHD plasma is the way (PS51D550). If you don't need SD/sport/motion go for a Samsung Series 5 LCD, the LA46D550 is R7,999 and might use the same panel as the Sony 46" CX520.
P.S. Wrong forum.