All the modern 90s are sharp.
The only thing I'll add is that you MAY get sharper results from a faster lens (f4.5 or 5.6) for two simple reasons.
1. you will be able to see the ground glass better which aids focusing.
2. When the 4.5 and 5.6 lenses are wide open for focusing they through the out of focus elements slightly more out of focus than an f8 model, which may also allow you to focus more accurately.
I used to use a 90mm SA f8 and switched to a 90mm Nikkor SW f4.5 for these reasons.
Assuming you are focused properly I believe all the modern 90s will give similar results.
Last edited by Shawn Dougherty; 09-20-2012 at 11:35 AM. Click to view previous post history.