Slayer is not the fastest way to train combat stats, but it does offer things to help you train other skills. I'll compare it to camping yaks/skeletons/bandits where the drops are minimal. Slayer offers a wide variety of charms, of all colors. If you eventually want to train summoning, but can't stand camping waterfiends or lobsters, slayer is a decent alternative. Slayer tasks is the only way to train slayer, if you eventually want a high level in slayer, you should start training it now to avoid going way over 13m xp in your combat stats. Higher level slayer will provide money. It isn't fast money, but it comes in. After around level 75 slayer with gargoyles you'll begin making money. On a recent Abby Demon task I was obscenely lucky with 5 whip drops. That's 7.5m in 2 hours. Not bad if you ask me. Slayer provides a slight variety. This is the big thing for me. You can do your tasks however you want be it melee, range, cannon, or chin. It keeps me from getting bored of click, hit, hit, hit, dead, click, hit....and so on and so forth. While training slayer, you get to use the black mask, though not as potent as the Slave Amulet (e) it can be used on everything (given you have the slayer helm).