I think hq4x has a slight edge because it doesn't go all the way trying to make everything smooth, still preserving some pixelation. There's actually an analog to this in denoising: if you denoise too heavily you end up losing detail. Smart denoising manages to preserve edges, giving a better result. In this case, pixels are the same as noise, undesirable, but containing useful information.
This method still wins out though.. but interesting never the less.