If size is that big of an issue.
In large tanks, I can't see the Nanostreams being much more aesthetically pleasing or space saving than the hydor koralias even at two times the length. I wouldn't say it is 2x the size. It's just longer, not really wider, so when you say 2x, I would be more specific and mention that it is really the length of the pump and a lot of that is due to the stem of the pump.
For the most part, I'm super pleased by both nanostream and hydor koralia. I was a little disappointed to find out that some user tests had only shown the tunze nanostream 6045 to yield roughly 930-950gph, which is far below their estimated gph via the manufacturer.
I expect that the hydor koralias (at least the 4 is actually above the 1200gph rating that is stated by hydor, although harder to test due to its very dispersed flow vs. the steams).
The test seemed to be a decent one, but prone to user bias, as it depends on the person to pull up on the tub as it is emptied. Still, he did take like 9 measurements and averaged it all out. The test seems to be precise, although accuracy is always debatable.
Cheers,
John