If you read these forums, I think you'll see that a lot of people have bad experiences with Sieos. I, on the other hand, have had only satisfaction with the three that I've owned and used for two years, each. On the one occasion that I had to deal with TAAM, they were actually very good and sent me the part that I accidentally broke myself. So, I have been completely satisfied with them, and I start and stop them whenever I put food in the reef. They always start up again immediately. I will say, though, that I've tried two Rios and they were useless and frustrating.
I've never heard anyone say anything bad about a Tunze and the Vortechs look mighty good. I particularly like the idea of keeping the motor out of the water so there is no heat generation from them.
So...there is some "gamble factor" with the Sieos that ought to be factored into your decision on which powerhead to buy...No gamble factor with the Tunzes. I don't know if there's enough of a track record on the Vortechs to say, yet, while their design is the best of them all, IMO.