A short description of both networks might help you.
Instagram - only pictures with no links (except for bio or plain text links in descriptions) you can still sell shoutouts and get paid to post products for companies. Mixed genders and demographics which works for various niches.
Pinterest - it's all about pinning content with beautiful tall images but they also send users to external links so it's easier to convert sales and amazing to get website traffic that really lasts if a pin goes viral. However, most Pinterest users are female so you need to choose your niche carefully (e.g. anything technology is very difficult to promote on Pinterest right now).
Basically you need to do your homework. Make a list of niches you'd be comfortable with, then check to see how well they're doing on both networks. Choose the right one(s) and you could benefit from having both Pinterest and Instagram accounts.