Well it probably depends on how "strict" you are being with the terminology and the specific technique you are refferring to.
"Mae-Ashi" really just means with the front/leading leg" whereas "Kizami" is loosely translated as "jab(bing) or snap(ping) but I think also has connotations of "cutting"" .
So for example you could perform (and indeed need to in the Dan grading syllabus I think) a Mae-ashi Yoko-Gere Kekomi but a Kizami Yoko-Gere Kekomi doesn't really make a lot of sense. So for front snap kicks like Make gere keage and mawashigeri you could use either term.
Hope that ramble makes some sense.
Jim