I assume you tested 4096 textures.
Whats about the FPS?
On 2048 textures in any case, I may not have measured frs with a program, but in missions I have not really felt any difference in performance. And I've flown on maps that have both a 1024 and a 2048 version of the same map. In mission there appears to be no discernible difference that I can experience ...
The 2048 maps do seem to load slower though, both in FMB and when an individual mission is loading, although I would not know of a way to measure that ...
To my surprise I did not notice any fps drop on my average system (NVidia 8600GT) with high rez textures, high rez trees and high rez skins.
Loading time of maps in FMB is longer with 2048 textures. That's for sure. But the few extra seconds of waiting is worth the huge quality improvement.
By the way, I remember an old discussion about 512 and 1024 size textures. That it didn't make sense to use 1024 sized textures and we should stick to default 512 size.
And now we are talking about 2048 and even 4096 (!!!) size.
With the high rez textures it is sometimes recommendable to nót index them as the loss of colours becomes noticable.
Which means that each 2048 texture becomes 12mb. Compare that with the default 256kb
Not to mention the included BumpH files and .tree files which adds up the total amount of mb's per high rez map.