I havent used both (only used the korillia's) but from everything I have read both are very good quality pumps. The tunze ones have been around forever and have proven reliability.
I have used the korillia nano's and the 1 and they do provide very good flow with low power consumption. One thing I have noticed with both the nano's and the 1 is that occasionally they get a build up of air in the impeller shaft which makes them a bit noisy. Just turning them on and off a couple of times sorts it out though and they are fine after that (they do seem to take a few days to settle in though).
So yeah, basically both are very good, personally if I could get the tunze ones locally I would probably have gone for them but I'am still very happy with the korillia ones (I have 3 that im using, the 2 nanos have been running for a year without any maintenance at all).