From 8-12 feet away, don't get anything less than 47" or you'll be extremely sorry. 55" would be ideal at that distance.
If you're sitting opposite a window, the 3SV is the far better choice since it has a semi-matte/diffused screen which negates reflections. To add, the 3SV is an amazing performer and its price makes it a tremendous value, thus its scarce supply.
Vizio XVT473SV: 47" FALD with 640 LED's and 160 Zones.
Seeking: 65"+ FALD UHD with 1,200+ LED's and 350+ Zones.