I am not aware of any creationists who deny speciation.
The difference is that evolutionists believe that changes are limitless, while creationists believe that there are limits.
If you what to extend this, it could be said that Darwinists (or neo Darwinists) believe that the process of random mutation and natural selection where responsible for most of the diversity of life, while creationists claim that only small bits of variation can be accounted by this mechanism. (not all evolutionists are Darwinists)
Sadly debates on this topic are typically based on semantic games, usually none of the sides present positive evidence for their case.
Scientists (not "darwinists" or "evolutonists")
do NOT think evolution is "limitless".
As for creationist belief in limits, we see a wide range
of notions as to where the limits might be, but-one
things we do NOT see is the faintest hint of any sort of
mechanism that says "so far, but no further".
So the creationist belief is faith based, unevidenced.
(not all evolutionists are Darwinists)
That is so, in fact, I dont think there has been one
anywhere since maybe about 1880.
Sadly debates on this topic are typically based on semantic games
Refraineth thou, then. from the game of introducing
invidious terms.
In the event, what is actually sad, from my pov, is
that the creationists invariably argue biblical
ideology, and have no competence to discuss maters
of science.
It is sad for a couple of reasons. Sad to see people debase
themselves, trying to uphold their faith with illogic
and ignorance, sad also, in that any field of knowledge
or research can always use people who raise reasoned
objections, and look for real errors.
The Challenger explosion, and the Hubble telescope
out-of-focus lens fiasco were times when a bit more
critical examination would have really paid off.
We are unaware of any useful contribution, ever,
by any creationist, to any aspect of science.
Please let us know if you are aware of any.