Between Tamron 17-50 2.8 and sigma 17-50 2.8 which is best for the Nikon d7000?

I had a 17-70 sigma which was great and sharp but when it comes to 17 wide it was soft at the corners even at f8 higher, also it takes in alot of battery usage, don't know why.Af was superb though, but i heard good things about the Tamron too but it has the vc and non vc and thats another question to go around. So anyone can help me decide on which is which on my Nikon d7000? I need sharp beautiful bokeh images. P. S Nikkors are just to expensive.

The best as you already know it is the more expensive one, the Nikkor. Between Sigma and Tamron, the former is a bit better. 17mm wide in a zoom lens constructed by a third-party lens maker and corners are soft. What would you expect? I doubt there would be an improvement with the shorter zoom version. Your best bet would be a single focal length lens but price would be mind boggling.