Sigma 50-500mm vs 150-500mm

Hello,
I am going to buy one or the other of these 2 lenses in the next few weeks to be used with my 1Ds mkII. The reviews I have read indicate the 50-500mm is a bit sharper than the 150-500mm. My question is if the images produced by these lenses are destined to be printed in sizes 8x10, 11x14 or 16x20 would you notice any difference in sharpness between the 2 lenses?
I will use the lens for landscape and some wildlife shots. I am leaning towards the 150-500mm because of the OS which will allow me to handhold it if I want to. Most times, however, I use a tripod with pan/tilt head for my landscapes. Your insight into this question will be most appreciated. Thank you.

Tim

well the 50-500mm is sharper all the way up. the 150-500mm is best at f8/f10 at 500mm +it has i/s built in the lens and the 50-500mm doesnt. if your not worried about i/s built in the lens, i would also consider the sigma 170-500mm, i have had 2 in pentax mount and one in nikon but in nikon it doesnt have no i,s unlike pentax has i/s built in the body, so i have the 150-500mm in nikon mount, i also had the 150-500mm in pentax which i had to sell my first 170-500mm to fund(mistake that was) sold it 1 month later and got another 170-500mm whcih is sharp at f6.3 at 500mm.

New image stabilised version of the 50-500 just announced at PMA.

The 50-500mm is brilliant on the 1DMkII, and IMO produces better results than the 150-500mm, the only advantage the 150-500mm had was OS, but with the introduction of the OS on the 50-500mm, i think the 50-500mm would be a better option. Just my 2 cents.
Regards,
Angad

Thanks everyone for your comments. I have to wait and see the cost of the new 50-500mm and comments on it's performance after which I will make my decision. One of those lenses will be purchased I just don't know which one as yet. Thank you again.

Tim