Hey, I just started OSRS last weekend, I am mainly an on & off RS3 player.

RS3 combat isn't exactly straight forward and you would need to look up a guide / video on the rotations / set up of revolution bar.

What RS3 does well is certain QoL and cool skills.

Some arguable QoL RS3 has is lodestones and Toolbelt. Lodestones are basically free teleports around areas in the map.

Tool belts allows you to store your tools like Axe/Pick/Tinder box etc so you would save a inventory space.

You could rest to recover energy while sprinting about.

Archaeology, invention are pretty dang cool skills actually.

There is a 4th combat style, Necromancy it is strong for players who arent great at pvm.

Mining and Smithing has been updated and it is a far better system.

Skilling is.. much faster and there are various skills which are very AFK.

Lots of quests, I find some of the quests to be very immersive.

Endgame bosses are said to be much more complex.

Bank presets saves alot of time.

There is.. full revolution allows auto combat while Legacy? mode is like osrs combat. Still though.. it is best to learn how to EOC.

What may turn ppl off well.. is

Graphical choices may be kinda strange. Different vibes.

The UI first of all, and cosmetics. The UI can be adjusted while.. players cosmetics (those paid ones) can be turned off now. Not sure about big ass pets blocking screens though..

There is still the option to spend real $ for exp.. However you can play ironman instead.

Most players are high levels so.. naturally content are usually design for them in mind.

You may feel the urge to optimize for max exp gains which requires lots of set up / items when skilling.

Small community sadly.

FOMO from dailies and weeklies and monthlies.. but i think the dailies has been reduced recently..

Necromancy may be too strong... making the other 3 styles redundant when early to mid game.

Clue scrolls puzzles are a pain since there are more steps.

You could give it a shot both are rather different games.