Partition or Map drives?

I am shortly replacing 3x 2Tb hard drives with a Western Digital Black 4Tb in a major reorganisation of my system. Currently my drives are not partitioned and folders have become badly organised as I was led to believe that partitioning wasn’t a good idea nowadays. A few folders are mapped to drive letters and I have a 3Tb NAS drive on my router for backup.

My question is whether to partition the new 4Tb drive or to create a folder structure and map some to drive letters?

I have a Win 8.1 setup with 16Gb RAM, an SSD boot drive and SATA6 and am a photographer so have very large files to move around at times.

Any comments welcomed.