It all comes down to what you are looking for specifically. For some people's applications vortech's are better, for some people, tunze will be better. My tank's going to have enclosed sides that will hide the external pump of a vortech, so for me, the low in tank profile works. You either have to have a big obnoxious cord in your tank or out of your tank - which is 'better' is up to you.
Yes, they make some noise, but it depends on what your noise threshold is. Like others here have said, my return pumps, skimmer, and the fan for my old MHs were way louder than the vortech's, so I don't know why the noise a vortech makes would be too much of a mark against it. I only ever heard my MP40's when I was sitting a few feet away as they were ramping up to full strength on reef crest mode, and even then I only noticed it for a second. To be honest I kind of liked hearing it - it wasn't an obnoxious sound and it let me know they were working for the money
They also don't transfer much by ways of heat to your water, which if you run halides can help.
never owned a tunze, but I hate, hate, hated the look of koralias in my tank when I had them, and they seem similar to me. Again, that's just a personal aesthetic thing.
So really, it just comes down to personal preference. They both move a vast volume of water around and are versatile in their controllability. The rest is just taste.