Nikon lens help

[Tokka]

I need help
I am going to buy a Sigma lens, either the 150-500 or the 50-500, the price i have found are reasonably the same, although the 50-500 has not got the optical stabaliser, although it is a faster lens at f4 as apposed to f5/6.
Need your opinions.
Many thanks,

[glsammy]

It's only F4 at the wider end. By the time your at the 500mm it's F6.3, so in that way there's little difference. If the wider end is useful to you, then that could be the deciding factor.
Personally I don't rate the OS, mind you I've only ever used two and one of them was an early Canon version. Provided you use some support, a monopod will do nicely, you should be able to manage without it. None of my lenses have it and I can't say I think I'm missing much. Don't forget the OS doesn't stop the subject movement.