The SL3 wins 3 of 8 scored specs (resolution, max video, weight); the A9 III wins 5 (burst, stabilization, battery (cipa)). The A9 III is $685 cheaper.
FRONT (WIDTH × HEIGHT)TOP (WIDTH × DEPTH), LENS FACING DOWN
Outer sizes are exact, from the makers' dimensions. Shapes are drawn by us to show each body style; the dashed circle is the lens mount at its real diameter.
BurstThe fastest frames per second the maker quotes. Top speeds often use the electronic shutter and may limit autofocus. Higher helps for sports, wildlife and kids.15 fps120 fpsBEST
StabilizationIn-body stabilisation. Each stop lets you shoot at half the shutter speed without blur, so 8 stops means very steady handheld shots.None8 stopsBEST
ShutterFastest mechanical and electronic shutter speeds. The silent electronic shutter can freeze faster motion, but may bend fast subjects on slower sensors.1/8000 mech · 1/16000 elecElectronic only, 1/80000
AutofocusWhat the camera recognises and tracks automatically, and how dark it can get before focus struggles (lower EV is better in low light).People, animalsPeople, animals, birds, insects, vehicles, aircraft, trains · down to −5 EV
VIDEO
Max videoThe highest video resolution it records internally.8KBEST4K
Best 4K frame rateThe fastest 4K frame rate. 60p and above lets you slow footage down smoothly, and 120p gives 5× slow motion.4K 60p4K 120p
Log profileA flat picture profile that keeps highlight and shadow detail for colour grading later.L-LogS-Log3
Raw videoRaw keeps the most image data for editing, at much larger file sizes. Some cameras only record it to an external recorder.None16-bit RAW via HDMI
Open gateRecords the whole sensor area, so you can crop the same clip to both widescreen and vertical video.YesNo
BODY & HANDLING
Battery (CIPA)Shots per charge on the CIPA standard test, using the rear screen. Real-world numbers are often higher.260 shots530 shotsBEST
WeightBody with battery and card, without a lens.0 gBEST702 g
ViewfinderElectronic viewfinder resolution and magnification. More dots and a bigger magnification give a sharper, larger view.5.76M-dot, 0.76×9.44M-dot, 0.9×
Rear screenFully articulating screens flip to the front for vlogging; tilting screens are quicker for photos at waist or overhead height.TiltingMulti-angle
Card slotsTwo slots let you record a backup copy at the same time, which matters for paid work like weddings.CFexpress B + SD UHS-II2x CFexpress A/SD UHS-II
SYSTEM
MountWhich lenses fit natively. Other lenses may work through an adapter.L-Mount AllianceSony E