1. I'd forget the G2 and go for the G1 version as I doubt that you would notice any difference, and save the price difference for something else. I had the G1 version and loved it and only sold it to fund my Sport lens.

2. Why would you want a 20 year old lens that weighs 1.3kg, has no stabilisation and is not as sharp as the Tamron. I must confess though to being wooed by it about 10 years ago, but came to my senses and bought a Sigma 70-200 f2.8 instead.