Social media isn’t thought to have too much of a direct influence on SEO.
By this I mean 100 Facebook likes won’t affect your ranking much. But obviously, social media drives engagement, traffic, and conversions, so it does have an indirect impact. Social factors are rising in importance, however – especially Google+ – which obviously impacts what people actually see in their results. Using some kind of automated service won’t impact SEO.
HOWEVER, I’ve found that it does impact engagement. Every time I use Hootsuite or Buffer, I get less engagement on my posts – even if it’s a video or image.
Lots of people swear by Edgar and CoSchedule. I haven’t tried them. There are also some good tools for sharing to Instagram and Pinterest.
Check out the useful links tabs for some of these tools. So, in short: no: zero impact on SEO. But IMHO they do impact engagement. That’s why I go for the old school Excel spreadsheet, open five tabs, cut and paste approach.