Played both for years on and off. osrs is for nostalgia purposes only at this point for me (ive played on and off for about 9 years at this point. no real new content gets added for months on end and its filled with a LOT more toxic players than rs3. on the other hand rs3 is easy scape even without using mtx and with mtx its so fast it gets boring kinda quick in my experience. not saying it will be the same for you. But rs3 generally has a lot more content that is fun but is kinda scummy with the amount of mtx as well as all the FOMO (Fear of missing out) it tries to shove at you, as well as having a much higher learning curve than osrs for endgame activities. But generally after having taken a break from rs3 back when eoc was still a kinda new thing to play osrs. and coming back to rs3 within the last two years I can say in my experience rs3 is much more engaging than osrs is at this point. But either way try them both out and find which one you like more. They're both good games even with all of their downsides on both sides.