The GS4 is using a PenTile screen (ugh) and the US version is NOT getting the Exynos Chip. I think the Note 2 will be snappier in day to day use. The Exynos Chip powering a 720 screen vs the Snapdragon on a 1080..1080 needs a lot of power. Though, I'm curious how the GPU's will stack up.
I really hate PenTile, also, there is no telling if Samsung has fixed the Antenna issues that has been on all their phones (except the N2, apparently). With the Moto X phone coming this summer and the Note 3 at the end of the year, I'm content to buy a Note 2 now off contract for $500 and sit on my upgrade to see what winter brings.
I also really wish they would have incorporated front facing speakers...