Eheim is way better than fluval, but rena is bomb for the money!! look up reviews yourself.. not the best not the worst but definitely worth the money.. mine has been great. for my 150 gallon though i'm going with the top of the line eheim.. just so i can say that's what i'm running, but other than bragging rights(and to give my fish the "best"...) they all get the job done so just buy the cheapest if your tight on money..... right?
****when i say buy cheapest... i mean out of those 3 companies mentioned