In essence pick the one that's cheaper mate.
They're both good psu's , neither will let you down.
They're going to be running 30% load with what you currently have , at that the seasonic will be slightly more efficient.
Upgrade wise ?? The corsair has around 50w more 12v available in the average build.
Which only really matters if your upgrades include a 250-300w GPU (unlikely unless you buy second hand stuff from a couple of generations ago)
For instance I'd be wary of running something like a 390x on the seasonic whereas I wouldn't have an issue with the corsair.
Everything blackbird says above is absolutely true BTW but the corsair is generally cheaper (a lot cheaper in the UK)