when you say the AC87 performed well in online gaming, were you playing while there was other substantial internet activity (downloads, youtube, etc) going on from other clients?
Yes. I had two console gaming systems playing COD: AW with no lag. I also had Netflix streaming through an Apple TV AND Netflix streaming 4K content through an HD Media Player. There were no issues with any of the four devices. I made sure to check the quality of the content being displayed by Netflix. There were no issues with quality on both devices (Apple TV was in HD / Media Player was 4K).
I suppose it would only be fair to try it on the 5500 as well.
I was able to swap out the AC87U for the 5500 and run the exact same test as above.
**I did notice, on three separate incidences, while playing COD: AW that there was some lag. It wasn't anything serious and it wasn't for more than a few seconds.
**Netflix being streamed via an Apple TV was in HD quality. No issues.
**Netflix being streamed via the Sony Ultra HD Media Player was not being streamed in 4K (it was the exact same show - Breaking Bad - that I used to test on the AC87U). I was getting HD quality, but for some reason it wouldn't stream in 4K.
I did stop the Netflix streaming via the Apple TV and noticed the HD quality on the Sony Ultra HD Media Player switch to 4K quality. There was no noticeable lag playing COD: AW on two gaming consoles. I once again began streaming Netflix via an Apple TV. The Netflix streaming on the Sony Ultra HD Media player had streaming issues and reverted to HD quality. It was noticed that some lag was experienced in COD: AW once again. It wasn't anything more than what was experienced before.
All in all, the 5500 seemed to handle everything very well. Not quite as good as the AC87U, but acceptable by my standards! I don't plan to ever have this exact set up (two gaming consoles / streaming 4K content / streaming HD content) all going at once, so the 5500 is certainly capable of handling most of what was thrown at it.
Now if D-Link would get their act together and provide a decent firmware that fixes issues and doesn't "break" perfectly working issues.
I'm sticking with the AC87U as the main router. The 5500 will go back as an AP for now.