I could be wrong, but I don't think there is a difference in its stock form. Most guys use the 34 for competition shooting, because of the slightly longer barrel, the extended slide release, and the longer distance between sights.
It is labeled as a Tactical/Practical on glocks website. I figure if it is a 'competition' 34, then it was because someone used it as such (and might have some modifications done by owner/gunshop).
Don't know if I answered your question, but I think they are one in the same.