EEG has been around for nearly 100 years. Apparently, the lack of spatial localization is a pretty big issue. fMRI at least holds the potential to be combined with small molecules and contrast agents to increase spatio-temporal resolution, as well as, being used to measure neurotransmitter levels directly.
Depends on what your goal is. If you're trying to work out a particular large-scale network, but are correct. BUT, even with 1mm^3 voxels, your spatial resolution still isn't that great and the time course of the BOLD response is pretty uninformative.