That there are settings in which magic or science is sufficiently advanced that either the science is coming into exploring principles that works parallel to physics or the magic is explained as further extension of science.
There are also settings in which seems like fantasical settings with magic but then revealed was actually a sci-fi universe and all the magic was just sci-fi technobabble which works by extension of real world physics instead of some separate principles.
But this is a pretty... well, it's a pointless dichotomy, really. No offense.
Historically, "magic" was considered a science -- it was thought to have its own distinct set of rules, and scholars explored it, experimented in the attempt of figuring out how processes worked to get desired results, and tried to replicate successful experiments. A lot of what was known as "magic" or "alchemy" laid the foundation for modern chemistry, for example, which is now unambiguously considered a science.
"Science" is not really an object, it's a
method. Stories may explain that magic is a manipulation of the natural world that seems to exist alongside, defy, or contradict reality, but magic in a story is "scientific" more because of the approach the characters take to learning, studying, and using it. Sure, you can write "magic" as a natural extension of existing physics concepts and natural laws (
Mass Effect comes to mind, with its attempt to justify what is more or less wizardry and magitech as gravity manipulation), but that is in my opinion quite silly, as "magic" can, was, and is studied in a scientific manner in the past and present.
Really, the distinction should not be between "magic" and "sci-fi", but between whether the "magic" (i.e. the ability to manipulate and change the world) is
controllable or
uncontrollable.
Controllable magic can be predicted and used by characters in a setting -- do thing X, and result Y happens. This is very much the standard of modern fantasy and I don't think I need to elaborate by naming examples.
Uncontrollable magic is a bit different -- this is where magic has some sort of factor that result in people being unable to predict and control it, perhaps having a mind of its own, meaning it cannot be controlled in expected ways by the characters.
The
Tortall universe comes to mind, where some magical abilities are favours from gods and can just as easily be taken away from or granted to pretty much anyone; another is
Discworld, where magic is basically such an unpredictable and dangerous mess that the wizards have stopped trying to do any and have just resigned themselves to academic hedonism, with witches being more social experts than magic users; and I also think
Dragon Age can fall into this category, as magic comes from another spiritual plane that is inhabited by actively malicious beings that prey on humanity, with implications that it has spawned the eternal plague that threatens to wipe out humanity and where wizards need to rely on emotional control to produce magic and are treated as ticking time bombs because of the danger of demonic possession.
Warhammer 40k and
Star Wars have similar approaches, as the magic can be studied and used by humans, but seem to really be beyond human control and its true understanding eludes human knowledge.
Another example are the works of magical realism, like
The House Of Ghosts by Isabel Allende. It's clear that there's
something magical or otherworldly going on in the background, with ghosts and the like, but the characters are left in the dark as to what it exactly it is and they have no control over it, being left at its mercy. In a more directly horror story way, the
Cthulhu Mythos by Lovecraft and its derivative comes to mind.
Many setting mix and match these two approaches in order to give the setting predictability and unpredictability in different doses.
Dungeons and Dragons has in its lore an approach of magic as predictable, understood science and also as ritualistic favours granted by gods (that players systematically minmax anyway lol);
Harry Dresden has a system of magic based on understood scientific principles that can be studied and applied, but also makes it clear that a lot of magic is undiscovered, dangerous, and manipulated by forces that humans cannot control and that may be actively hostile to humanity's existence;
Harry Potter has a mostly academic system of magic where some core principles are nonetheless beyond direct human control or influence (the Department of Mysteries demonstrates this, and "Love" being considered the greatest and most terrible power of all).
...Really, come to think of it, most fantasy stories (and others with magic-like systems) seem to mix both approaches, with differences being a matter of degree.
Honestly, the oh-so-common science/fantasy dichotomy is rather banal and not especially useful for this discussion. What's more relevant when thinking about magic "systems" in terms of writing and worldbuilding fiction is whether they are actually
controllable and thus
to what degree it can be manipulated by the characters.
In many ways, "sci-fi magic" can be controllable and uncontrollable as well --
Mass Effect comes to mind, with biotics being extensively studied and used, but a lot of the basic principles of eezo manipulation are beyond the sentient races' control.
Star Wars has mostly controllable "magic" that seems to exist independently of human influence, but where focus and study allows a degree of manipulation.
Star Trek has a high degree of controllable "magic" based on allegedly scientific principles, but there are still beings with the power to manipulate reality in ways that defy human understanding and elude human control.
In many ways, modern science may well appear to be magic: we understand a lot of the physical laws of this universe and can manipulate it to a certain degree with input X getting us output Y, but we nonetheless are at its mercy in many,
many ways. Hence why many sci-fi concepts are very analogous to "magic" systems, and as you can probably tell by now, I find the distinction rather immaterial.
Hence
the degree of control the characters have over the ability to manipulate their world seems like a more useful distinction. At least when talking about fiction.