Four Union Volunteer elements cost the same as three Conscript or Line infantry elements. The problem with this is that the volunteers only have an initiative/discipline of 6/6 whereas the conscripts have 7/7 and the line infantry 9/9. However, McClellan, Halleck and Sigel can each train two volunteer elements per turn so that they become Volunteer-line infantry (V-line) with an initiative/discipline of 8/8. So with a bit of organization, the Union player can get a little more bang for the buck. But are V-line elements worth the extra effort?
Initiative determines which element fires first. From the AGE Wiki:
"The order of fire is determined by the initiative-values of the elements: elements with higher initiative are likely to open fire before elements with lower initiative (there is a random factor involved though!)."
So the difference between an initiative of 8 in the V-line element and a 9 in regular line infantry probably isn't too critical.
Discipline affects a factor called Troop Quality Modifier (TQM), which is:
1 + (discipline - 5) x 0.05
For 8 that would be 3 x 0.05 = 0.15 whereas for 9 it would be 4 x 0.05 = 0.20. So the difference between the two would be 0.05. The TQM is multiplied by several other factors to produce the final to hit chance. If the other factors produced a chance of 20% to hit then a unit with a discipline of 9 would get (0.2 x 0.05=0.01) a 1% greater chance to hit than a unit with an 8.
Thus, the V-liners are almost as good as the regular line infantry. After spring 1862, you can produce 6 V-line infantry per turn for more than a year, whereas line infantry usually come mixed in with conscripts or other elements. I leave McClellan in Cincinnati to train a stack of volunteers from all over the Midwest and move Halleck there to assist with his own stack. This gets me a total of about 40 V-line infantry elements in 1862. When Sigel arrives, I rail them to NYC where each can train a stack of volunteers from all over New England. This gives me a steady supply of good infantry to fill out Division cores.