Why did Janeway act like a warrior? Why was Picard so diplomatic? Why were Archer and Kirk so vigilant when it came to shoot first ask questions later? I believe that some of it can be answered by the size of the ship and the size of the crew.
Archer cried over each man lost because his crew wasn't a large one, his ship was the first and it was small as well. Kirk had one of the smallest ships but for some reason had a gigantic crew compliment. My guess? He couldn't get rid of people quick enough. He was practically pushing people in front of lasers just to make some room on that tiny ship of his...
In the words of Jordi LaForge in his days with future reading rainbow, "but you don't have to take my word for it:
USS Enterprise E (Picard movies)
2,055 ft long
Crew Compliment: 500
USS Enterprise D (Picard TNG): 1926 ft. Long
Crew Compliment: 1,014
USS Voyager: 1002 ft long
Standard Compliment: 141
Actual compliment on mission: 146
USS Enterprise (Kirk): 867 ft long
Compliment: 430
NX-01 Enterprise (Archer): 675 ft. Long
Compliment: 83
http://www.st-minutiae.com/misc/comparison/comparison_medium.png