They are both interesting platforms with different targeted audience.
Steemit has been around longer and has many more users. Its primary function is blogging on a wide variety of topics like cryptocurrency, travel and philosophy. It has a lot more developers working on it and many apps have been around the Steemit ecosystem. The main currency here is STEEM which can be powered up to STEEM POWER.
Scorum is specifically a sports blogging platform, fairly new (not much older than 2 months), and is geared towards those who want to really engage with other sports fans. The visual interface and site looks clean and is much more appealing than Steemit. The main currency here is Scorum Coin (SCR) which can be converted to SCORUM POWER.
Both the platforms reward authors and curators in similar fashion. If you are active in the community and do quality blogging, commenting and posting, you will get rewards.