No recent experience with Fluval or Marineland Emperor, but I now swear by AC 110 HOB's for a discus tank. The only drawback is that being HOB's, they're not out of sight like canisters.
But to me, that's a definite advantage.
I have 2 110's on my 75 gal discus tank and can't say enough good about them.
They're efficient and reliable, easy to keep clean, very versatile in terms of ready ability to cleanse, interchange, or replace media, large compartmentation, easily serviced and maintained, as well as quite quiet if you do keep them well-maintained.
Highly recommend.