Ok, objective.
Width would be one. It’s one of my most noticeable factors now, having actually carried the G19, 26, 43X and 48. It’s hard to quantify exactly why it makes such a difference to me, but it does. Perhaps stature plays a role? (I’m 5’6”). Possibly larger humans feel fine with a double stack gun (I.e. wider) because they are bigger. “To me”, the 43X/48 width just offers that much more comfort in traditional IWB, AOWB, and AIWB (done them all). Whether it would matter to you might thus depend on how large you are.
Grip length would be another. There’s no doubt a G26 with an OEM round mag is a two-finder Grip. Can you shoot it accurately? Yep. Ask @GAP. He can shoot the lights out with a G26. And so can many others. It’s often reported as one of Glock’s most accurate guns. But you might make note of how many carry a G26 with +2 mags. Hint: it’s not always because of added capacity, they want a pinky rest, I carried my G26 12+1 as well, so I get it. (This was about the point I decided I might as well carry my G19 15+1.)
The longer grip length of the G43X/48 affords a full three finger grip for my size M hands. Rapid reloads are considerably easier as well.
Rail vs no rail. The G26 does not have a light rail, afaik. (Mine didn’t). The G48 FR recently introduced does.
Trigger reach. This is going to depend on your anthropometrics / hand geometry. A G26 stubby fat grip might suit you fine, or the longer slimmer G48 grip might feel considerably better, shooting, So while they are objectively different in this area, it’s going to depend on you and how you shoot them.
1 vs. 2 slide catch/releases. The G26 has a stop/release on both sides. The slim line G48 only has a stop on the left, since it is too narrow to allow figment of the Gen 5 part.
Sight radius. I find the longer sight radius of the G48 to aid in slide alignment and may contribute to more accurate follow up shots. I don’t perceive any disadvantage in concealment with the 4” barrel, either. In fact the slide length doesn’t really enter into whether or not I can conceal the gun; it’s more about grip length and thickness.
I will say the G26 carried ok for me in a pocket Desantis Nemesis, albeit it was a little porky. I can’t pocket carry a G48.
They are both excellent choices however. It really depends on what you are looking for.