I have 3 emperors and 4 ac 110s running now.Both are quiet and do the job.For those of you that think one makes more noise than the other,break out the owners manual,you are doing something wrong.If water moving noise is the issue,snakes or hamsters may be a better choice.

The emperors are more likely to restart without help after a waterchange,the 110s often needs some water poured in to get it going.
The emperor is more solidly built,the ac plastic housing is a more fragile plastic.Not really an issue,it hangs behind the tank,its not an atv.
The main problem I have with the ac is the cheap little plastic foot that keeps it aligned.If something knocks it off the filter will spill water on the floor.
Ive modified my emperors to use quilt batting and sponges so Im not buying the expensive replacement pads.
What would I buy next?Either. Whichever I could get a better deal on next time I need filters.Like I said both are quiet and do the job.