I run 3 FX6 on various tanks including a 125 and 135 and am very happy with their performance. I dont have any experience with the Eheim. I have the fluvals full of matrix and clean them around once a month.
Is it a necessity to clean them every month? From reading some previous posts on the 2262 (Harley K etc) it looks like the eheim has a significantly longer service time if it is set up right. I don't mind servicing a filter every month (I do it currently) but I figure the less you disturb you bb the better off they are.