Look at it this way, if you ask for advice, be prepared to take it, unless you think you know the answer anyway , in which case asking for advice is pretty pointless.
In this case, you said you wanted something fairly simple. The One is simple and most people have offered that as a good buy, even all the techie mags say its the best of the bunch. The 510 might come with extra features, but you admit to being a little techologically challenged at times, so if extra features mean extra compexity that in turn means more possibility of something going wrong.
Off back to sleep now.
Night everyone
