If it's kino then I buy the olympia but don't use it til round 5, it's great fun! M14 is better for points but i love blowing zombags away with the shotgun. On "five" I wait til I can buy the first doors then buy the mp40 or whatever it is, good for points!
90% of the time i dont buy either, but if my teamates really suck or it gets hectic i always get the m14. it gets you wayyy more points then the olympia, and the reload on the shotgun is just to brutal