Tamron 70-200/2.8 with 1.4 TC or Sony 70-300?

[Yagil Henkin]

Hi!
I'm wanting to buy a midrange zoom to use on my A700 and on a future Full-frame, and I'm wondering which one of those is better. The tamron is very tempting, as it is 2.8 and with a 1.4TC It's basically a 100-280 f/4 lens - not bad at all. The image quality w/o TC is said to be excellent on full frame too. On the other hand, the sony is lighter, some say better and faster focusing, and I didn't see any comparisons, Bokeh-wise. I'll be very happy for any information - both on the speed, quality and Bokeh, especially on the A900. SLRGear tested it only on 12 mp camera (D3), and I'm wondering how those lenses stand up against each other on the A900 in terms of overall quality, focus speed and bokeh. Also, anyone who used the Tamron with a TC and can comment on the effect on Image quality and focusing speed, I'll be very happy to hear the verdict on that.
Thanks!