I like them both for what they each have to offer..... The vortech moves massive amounts of water, has its own controller, connects wirelessly with other devices, and has a low profile... Downsides would be, some people find them noisy, the wet sides are a touch fragile, you are limited as to where you can mount them(unless you get creative) and you can't point them.... The tunzes move a decent amount of water, can be mounted anywhere, are pointable and are bulletproof.....downside would be the profile inside the aquarium...
I use them both
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260g mixed reef, 105g sump, water blaster 7000 return, Bubble King SM 300 skimmer, Aqua Controller Jr, 4 radions, 3 Tunze 6055s,1 tunze 6065, 2 Vortech MP40s, Vortech MP20, Tunze ATO, GHL SA2 doser, 2 TLF reactors (1 carbon, 1 rowa).
http://www.canreef.com/vbulletin/showthread.php?t=50034 . Tank Video here
http://www.vimeo.com/2304609 and here
http://www.vimeo.com/16591694