Hmm... I would prefer Science fantasy more than Science fiction. The more specific ones are those set in other realities, or other universes. They give a relief from our reality bound by laws and reasons by defying them. I don't read books on fictions and fantasy, but I prefer to watch in movies and series.

Both

I love both science fiction and science fantasy my current series I'm listening to on Audible is schooled in Magic by Christopher G. Nuttall. A girl gets summoned from Earth by a necromancer in another Realm and some of the things she comes up with magic wise from what she knows about science from Earth is quite interesting.

Both. But SciFi if I had to pick one.

The Science fiction section in my local library is down to one and a half shelves, from 10 shelves when I moved here 30 years ago. And most of those are like the 17th installment of The Gzornenplatz Universe. And two really great SF books (actually one book and one rapid-fire trilogy), The book of Good New Things and the Southern Reach trilogy are not listed as SF. I blame Harlan Ellison for this.

Why would one have to choose, both are great

It might be a function of getting older, but I can hardly bear to read fantasy anymore.

If the book doesn't touch on or reveal some sort of understanding of physics, history, etc, it gets binned.

Life is too amazing to miss out on learning more about it.

Either as long as I enjoy the characters and story.

There's a place for and I like both, but a lot of the time they overlap anyway. But would we need to differentiate and have Sci-Fi and Sci-Fa?

I read/write both. Isaac Asimov, Iain M. Banks, Douglas Adams are some of my favourites.

Philip K. Dick, Robert Heinlein, Jules Verne, Arthur C. Clarke, Larry Niven. My take on these guys are Science Fiction someday to be Science Fact. Even the original Star Trek had stuff that was fiction then, but fact now. The tablet computer he signs whenever the Yoeman comes around for instance. I even proposed a phone called the 'the communicator' for a startup telecom, basically a flip phone that looks like Kirk's communicator. Think about this - smart phones today are more advanced than the fictional communicator in Star Trek!

SciFi. Arthur C Clarke. Stephen Baxter.

It depends on my mood. Lately it's been sci-fi horror for me, which could go either way depending on the writer or story.

Both are fine. I tend to steer clear of shared universe/franchise books unless I can't find something else.

If a book has a lot of "hard scifi" science stuff it needs to be consistent enough that I don't feel like there are holes in it, locally.

I love all kinds of fiction, when I have time to read....which isn't that often.

I always prefer the plausibility of science fiction if I want fantasy i prefer it be along the mythological line.

I am a hard SciFi fan all the way, I have started reading a novel and suddenly some Grand High Exalted Mystic Ruler comes along and invokes the God of Hixlumee and saves the day. Yuk!
My favorite novels are about Generation Ships. Some of the old classics are; Non-Stop by Brian Aldiss, Orphans of the Sky by R. Heinlein, Captive Universe by Harry Harrison. There is a website somewhere that has an up to date list.

So where does Anne McCaffrey fall? Currently rereading "To Ride Pegasus". Written as SF but feels fantasy. I think the distinction is so artificial as to be meaningless anywhere but the extremes. Add to that the burgeoning plethora of sub-genres (military SF, Urban Fantasy etc) and the reading rapidly becomes more about taxonomy than entertainment.

Science fantasy "well of souls" series, and "Lord of Light" well worth reading
Sci fi, I recently read the "Gap" series, first time I read a strait sci fi since my teens, it was good.

I only read reality

Depends on the system. Things must be logical for its universe and rules must stay consistent. I do love Seaman McGuire and Tom Holt and James Alan Gardner and Scott Westerfeld for how they construct their worlds.

Science fiction is Arthur c Clarke,Rendezvous with Rama , Science fantasy is Dune by Frank Herbert