I work in retail with these tanks....
At the top you would find Ehiem and Rena. Both cost alot more than the competitors but there so much classier it's worth it.
Fluval and Juwel are about the same really. Both use the same build system for cabinets, light units are about the same, although we get a lot more Juwel light unit returns. The only differences are the actual visual design and filtration. Plus the push to open doors on the Fluvals are pretty smart. Although I hate fluval externals I'd probably buy a fluval.