I've used all of them also.
The Koralias are crap IMO-used a 1 and 3 and while the flow is alright, aesthetically they look terrible.
MJmods move some serious water but are eyesores
The Tunze nanos are a mix bag--they will break but they will also be fixed by Roger. I have purchased 4 6025s over the last 1.5 years and I've gone through literally 8 or 10 motor blocks and the same numbers of C clips. That being said, all the newest ones have been rock solid except sometimes they still dont start properly.
The Bigger Tunzes are very nice IMO, directional flow, no noise with great controls but they are big and pretty ugly. They also cost a good deal of money.
The Vortech is also great. Minimally intrusive, great flow and controls, but like Wes stated not directional. IMO they dont need to be. Also, my tank background is black and its very very difficult to even see it back there. They are surprisingly noisy though, even with the Gen2 magnet.
Anyway I am now using a mix...Vortech on one side, 2 nano streams on the other, and a MJmod across the back. I'll be replacing the nano's with another Vortech soon...
Forgot to add, if you havent seen what Tunze has coming out over the next year, you need to read up!! (mini wave box, nano-sized regular streams, etc)