The Seasonic 520 and 620w platforms sold by Seasonic, Antec and others, have been used for years and years and so far the often cried about crossloading issues have never been widely (Or at all in most cases) reported or experienced despite there technically being a potential for it. I myself have two or three of them that were used heavily for years. No such issues were ever evident. Yes, it could happen. No, it does not ever seem to happen for most people, at least not to the degree that it is a problem because if it was a problem that was likely or was being seen in droves like people seem to think it is, Seasonic would have been run under the bus long ago for it. As would others with group regulated designs. Many group regulated designs.
I get tired of hearing the unwarranted cries from the PSU snobs about these platforms. These particular ones, are still very solid for what they are and in some cases they are easily the best of what is available especially for specific regions. I wouldn't recommend somebody to use one of them IF there are other realistic options available, but I would not recommend against them either in cases where they are clearly the best choice and in this case given the two units offered as choices, they are the best choice. By far.