you dont have live plants so i dont see any point in the spray bar. IYO whats wrong with the 305s? Ive had no issues, just wondered why you dont like them.
As for the tetra extrenals, they have a really fragile looking bend to hook over the side of the tank, and if you have a decent hood on a large tank (like on my 6x2x2, which has a wooden lid) the bend just wouldnt fit, and they also use smooth clear pipes which are very thin, so they have to pump harder to get the same water through put as a fluval which has larger pipes.
there was one make which if Id had to the cash for i would have probablly gotten instead of the fluvals, as they have built in heaters, but they con you by not providing the filter media, which is so damned expensive it seem pointless owning one of the filters. For the life of me i cant remeber what brand they were