Hi. I have 2 fluval 306's running and one cascade 1000. The cascade also had mixed reviews, but I needed a big one and got it for a steal. I guess I'm partial to the fluvals. The build, the plastic, clips etc all feel solid. I don't get the same 'feel' about the cascade. It is mostly that clear hard plastic and that stuff tells me in the long run , it may / may not fracture as it ages. I do however like that you can see inside/trays to keep track of it.
So, never any issue with the fluvals. One issue so far priming the cascade. But that may have been me/error too. All three are whisper quiet, each has 3 large trays for media. The fluval has double the cell sponge of the cascade. The cascade comes with a nice long spray bar kit, where the fluval does not (but it should!) The cascade does not come with bio, only sponge and charcoal. Fluval has all three. But of course I have added more bio to all three as well as floss.
So, I would buy either one again, but in another post recently, as I stated, I will never pay full price. Always sales and rewards. My LFS
is WAY to full retail price on equipment.
I too read all reviews, but I'm very suspect of ones that claim they leak all over. I almost guarantee it's operator error. My first fluval I installed the big o ring wrong. Water everywhere. Completely my fault. Some people rather blame than state they didn't read properly!
Sorry not much experience with Eheim, although I do have their battery gravel filter. I'm not overly impressed with it.