The banding issue was apparent in 42, 46, and 52 inch models in the 64U series. However, it's not like 100% of the TVs had banding, and of course the problem varied in severity. I have seen plenty of perfectly fine 64U series sets, and several of my friends own them (although I don't know anyone with a 52). The smaller sharp sets didn't have the banding issue (IE: the 32"). Furthermore, banding was much less of a problem on the 64U series when compared to the 62U series. As for the SD picture, I personally don't think it looks worse than average. Other than the store models I have seen, the majority of them have been running Comcast digital cable, and the SD digital channels were quite fine. I don't think you can ever really trust what people say about SD lol... it almost seems like there are "worse than average" comments about every HD-TV set on the market when it comes to how they handle SD. People just don't realize how much better HD is until they try it.... then they say how much SD sucks on their TV. For the most part, everyone I know that owns one of the sharp TVs likes it (though it only amounts to half a dozen or so sets in the local area - many people got the CC black Friday deal on the 46).
I only say to consider the Samsung sets because of the current prices. The 4071F is currently being sold for $1450 on Amazon. You do future proof yourself with that 120hz set a bit more, as it's newer tech than the 64U series. It also has better PQ, better blacks, and a bit more adjustability. However, I'm not trying to suggest that the 64U is a bad set at all (it's still one of the better LCDs all things considered). But for the relative price difference, I would probably go towards the Samsung, unless you are getting the 64U for much less than Amazon is currently selling it for (I think it's about $1325 right now).