I have the 16-80, have been pretty happy with it.
Image quality is usually pretty great, build quality is just OK.
A few things I would consider,
at 50mm the Sony will be at 4.5, the tamron 2.8
at 16mm the Sony will be at 3.5, the tamron 2.8
at 80mm the Sony will be at 4.5, the tamron will still be at 50mm
I also look at Zoom lenses as two lenses, there widest and there longest
So the Tamron would be a 17mm 2.8 and a 50mm 2.8
I would ask myself would I ever use a 17mm at 2.8, maybe but not as much as I would think.
I would ask myself would I use a 50mm at 2.8, yes I would, probably a lot, but that is why I have a 50mm 1.4, I see you have a 50mm 1.8, so

As with a lot of people I replaced my kit lens with the 16-80, this gave me a slightly wider view and a noticeable longer reach over the 18-70, would the tamron be replacing your kit lens? Would the decrease in reach bother you?
I looked at some of your flickr photos and it looks to me most are outdoors, so I would assume that you would prefer a longer reach on a lens and that a larger aperture wouldn't necessarily be a benefit to you and your landscape photography.
Just a couple things to consider, it's obviously up to you.
So in a straight up competition which would I get, I would get the 16-80, well I have got it.
If you do a lot of low light shooting then the tamron could be a better choice otherwise I would go for image quality and reach.