Here's a comment i found from someone that has had both.
i had an fx5 my roma 240 which i recently sold, i now have 2 eheim pro 3 2080's on my 7 foot tank.
i can only comment on the 2080 as i have no experience with the 2075 but they are similar, the 2080 is just the next one up.
the eheims are good filters, easy to maintain etc, the fx5 was excellent, i want another to add to my 2 eheims!
the fx5 had a lot better flow rate, the eheims were a bit disappointing in all honesty. the eheims are slightly quieter aswel, but if its flow rate you want than that of the fx5 would over ride the extra humming noise, you can only hear it in a silent room. the fx5 is also about half the price, which is what first tempted me to get mine.
at the end of the day it depends how much you want to spend, you can get the fx5 new for around £130 and the 2075 about £160, if its flow you want id go for the fx5, if its reputation and german build quality go for the eheim!