One reason that could cause say one regiment being more efficent then another would be the political motivation of its officers. If an officer is more fired up about a given cause then perhaps his men might also become more likely to want to mix it up with the enemy. Lt James Pond of the 3rd Wis Cav USV might fit this mold. Per wlhn.org fond du luc "Fairweather Reports" or just type in Lt James Pond 3rd Wis Cav on google Lt. Pond fought one year under John Browns Command. Such an experience could result in a more zealous officer. The 3rd Wis per the ORs fought well in Mo, Ark and the IT. Lt Pond also was decorated with Medal of Honor for his efficent use of the sole cannon at Ft. Baxter during Quantrills raid.
Leonard