I don't know about the "bang for the buck" but the Oceanic Biocube has the best fit and finish of any I've seen to date (Nanocube,Aquapod,and Biozone.)
It also has some features that are improvements over its predecessors listed above. An easily removable mechanical/ chemical filter cartridge that can be removed / replaced easily without jamming your hand deep into the filter chamber. A surface skimming inlet with a subsurface inlet that's designed to work in conjunction with the surface skimmer. Remote ballasts on quick disconnects so the heat from the ballasts are not transferred into the aquarium. The ballasts have mounting attachments that allow you to mount then to a stand/wall if one chooses. A inlet and outlet fan in the hood. A well thought out drip plate design for the bio filter, A water level view port on the side of the unit to monitor the level in the filter chamber. A nice instruction manual with a replacement parts list with part numbers, and a good warranty backed by a well known company.
So it seems to me to be the nicest unit to date.
Aqua Medics Nanowave and Red Seas Max look like they may trump the Oceanic unit in features but their releases are as yet to be announced.