Both (PoE and D3 RoS - I hated Vanilla) are excellent games, we are spoiled for choice. Having played many hundreds of hours of both, they massage different parts of my brain. I have found PoE more about build planning, wealth creation and trading. The highs are higher and the lows lower in PoE. The feeling of 6-linking an item or chancing an amazing Unique is like nothing I've experienced in D3. Similarly, the frustration and desire to hurl my laptop into my TV when dying in your 90s or getting desync'd is equally negative.
I have found D3 more about gameplay gratification and (manual) skill. I spend a much greater % of my actual time in-game in d3 actually playing, and less time trading or build planning.
D3 is about play->find->build. PoE is about build->trade->play. I've found D3 to be more Action-oriented, and PoE to be more RPG/strategy oriented (although not so in actual gameplay, more in design/build). Both extremely fun, but sufficiently different experiences to warrant playing both.