A lot will depend on the surfaces you ride - or actually walk/run - on. Trails around here tend to be either loamy when they're new or bony/rocky as they get worn. Roads are typically either packed dirt or a combination of sand/gravel/rocks, with leaves, sticks, and pine needles thrown in for added fun. In the winter, there's snow and ice to contend with as well.
I've found that soccer and golf-style plastic/aluminum spikes to be basically useless, as they aren't aggressive enough to provide meaningful traction on most soft surfaces and they skate and slide on hard surfaces. Steel 'cross studs can be helpful on packed snow and ice and I use them on my winter cycling boots (Lake 303s), but they're really sketchy on rocks, pavement, and metal surfaces like cattle guards. I don't use studs at all in the warmer months, as the best material for gripping most surfaces is plain ol' rubber. Studs really don't help and are often detrimental to traction.
Steel and aluminum studs are very effective at damaging floors, which is another reason not to use them.