The current raids 1 is a very abstract version of Dungeoneering with a narrower scope of theme and less of an emphasis on skill use and puzzle solving.
Dungeoneering, as it stands, lets you explore separate levels of dungeons, each one uniquely generated with skill checks, puzzle rooms, battle rooms, resource rooms and boss rooms. You get experience based on your clear speed, your dungeon completion and your deaths. There are several different sets of dungeons which change based on how far you get. Dungeons are generated based on your combat and your skills, with some challenges you can complete and some you cannot.
Similarities between Raids 1 and Dungeoneering include randomized levels (raids 1 being way less random than dungeoneering though), gauntlets of bosses (with dungeoeering having a boss fight at the end of every dungeon), a rewards system based on points earned and points earned based on performance (raids 1 gives better chance at a reward as your points go up, dungeoneering gives you 10% of exp gained as tokens, which can buy permanent or temporary rewards), and the ability to run solo or run dungeons with a team.
If you were to ever going to log in to RS3 again to do anything, I would suggest doing dungeoneering. Its definitely a skill in minigame form but holy shit is it fun.