Re-reading my previous post, it was unclear.
I'd go for the D. It has perfect specs, it is going to sparkle a lot because it has a superb cut and at 1.24 ct, I think it is a very large stone. I love the icy whiteness of F and up and to me the added size of the J would not be worth it.
However, if you want to be sure of being the most admired in 'most' circumstances, go for the J. When you buy a stone for beauty be aware that you are buying it for your own pleasure, since in my experience 9 out of 10 women (in America anyway) are always going to notice/admire the largest stone over any thing else, always, not the prettiest (unless the the largest stone has obvious, visible black boogers or doesn't sparkle AT ALL). The J in this case is certainly going to be pretty (it's very well cut) and it being over 2 carats gives you a very good chance of it being the largest stone, most of the time in most places (this would even include among lawyers and investment bankers in NYC in my experience) which does seem to be what really, really counts, when people are being absolutely honest. 1.24 doesn't do that anymore--it's a big stone (average is still .38) but it's not all that much bigger than 1 carat, which a significant amount of people now own.