I just made an experiment: 
 
I wrote 5 arbitrary set of values on a paper that when added together would equal 100. I used a stopwatch and using the production wheel I dialed in the exact values and noted the time it took . I repeated 5 times.
I then did the same using the 3 sliders in GalCiv 2
The values were : (35%,25%,40%),(17%,42%,41%),(28%,36%,36%),(7%,15%,78%),(54%,28%,18%)
 
Times for Production wheel:  1:50 , 1:17, 1:00, 1:07, 0:55  Average Time : 1:14
Times for Sliders :  1:18,0:57,0:57,0:55,0:51 Average time : 1:00
 
So at first glance it seems the sliders are actually faster to use to dial in exact values.
 
 
I made several interesting observations.
 
1.I was getting better with each try ( no brainer )
2.The first try with the wheel was significantly harder than the rest.
3.Using the wheel required more mental efforts, I actually had to think where I needed to put the dot while with the slider it was a purely mechanical task.
4.Most of the time consumed with the wheel was from trying to get exact values, ( getting roughly the right values was much quickler )
5. Dialing in symmetric values i.e (28%,36%,36%) is very easy on the wheel, compared to asymmetric values like (54%,28%,18%). On the sliders this does not really change anything.