The same arguments can apply to either raster or vector. For both cases I think there is sufficient distinction use between the noun and the act of converting to to justify having two tags. I don't think rasterize should have been made synonym for raster. While convert is also a tag, it seems silly to have a question tagged both raster and convert when it could just be rasterize.
My proposal would be to have raster, rasterization, vector, and vectorization. The tag rasterize should be decoupled from raster and attached to rasterization.
English 'z' vs 's' aside, pick whatever. "ize" is shorter than "ization" or "ising". And while I opened a can of worms in resample/resampling with the whole "ing" thing, and suggested there that we might follow whatever majority tag use was, I'm throwing that out the window here in favor of consistency.
I am a little iffy on the fate of raster-conversion since that seems to imply it also encompasses going from one raster format to another. In that case using the two tag approach seems more appropriate rather than a hyphenated tag. But I'll defer to others on leaving it alone as a tag, as PolyGeo's Wiki edit (with a bit of tweaking once the others are determined) goes a long way to improving its usefulness.