Depends the length, if you're frequently just weaving on and off, and only staying on for short sections (not one long stretch) then go for some spikes, you'll definitely reap the rewards. If you can afford it, go with both flats and spikes, for xc I recommend the Zoom Streak LT3s/LT4s, and the Nike Zoom Victory XC 4s, both super high quality and lasted me one extended season, as I race XC from summer until mid winter. If you can only afford one, grab the Zoom Victory XC 4s, and buy some track spike blanks online, and boom best of both worlds, it'll give you some extra grip, but you won't get the feeling that your spikes are sliding around underneath your foot.
Going by your name, if you're running slower than, or equal to, 20 minute per 5k, or the equivalent of whatever distance you're running, you likely won't feel a massive difference. I'd say once you start dipping sub 17 you'll really feel it. As a sub-16 guy myself, spikes are a must have for the lightness and added grip, around the sharp turns so prevalent in XC courses.