I am trying to make the same decision, well substitute the acer for something else, but basically the same ordeal. I have never used a LCD for gaming and am wondering if the E228WFP is a good gaming screen.
As to your question, personally i don't know, but I would assume that if you ever need to return the screen on the manufacturer's warranty, Dell will be more accessible and easier to deal with as opposed to acer. That's my 2 cents.