I've got three 404B's, and like them. As mentioned the intake/output is a bit flimsy but it is functional, the vinyl tubing is fine, and the filter itself to me is a straightfoward, simple design that works OK. Some bypass perhaps, and as mentioned the UV is more gimmick than otherwise due to the flow rate, but it's also not adding to the price significantly.
And LOTS of media room, and nicely quiet. I had one fluval 304, and got three 404B's instead of another fluval. The fluval continued to slow down due to some aspect of how the impeller cover was designed (at least I think so) that it warps, so when it was time to get more, I opted for the low cost and was pleasantly surprised.
As with all filters that I've seen, the specified flow rate is badly exaggerated. I found the 404B to be about twice the Fluval 306 I have.