To decide to partition or not you need to decide if it will help you.

Typically speaking OS drives get very fragmented due to constant caching and activity. Also if you have a full scale OS choke it's always better to have just your OS isolated by itself without your private files needing to be hand plucked out in DOS and copied over (if even possible and not corrupted).

As a general rule of thumb for last entire decade I always keep my OS on it's own partition. I use another partition for all my application installs. Then use additional partitions for other purposes. Storage / Video Editing / Video game archive / etc, etc.

Beyond the obvious benefits of organization of files by data type...the OS partition isolation has saved my butt more times than I can count over the years. It's great being able to use an image restoration software (something like Acronis) and be back up and running and still have all my private data unharmed on a secondary drive.

When your data sits off on a side partition (on a totally different drive from OS) it has a better chance to survive cataclysmic events.