I am 85 slayer so i've experienced both. Basilisk are one of the best monster for low lvl slayers. Quick xp because of low def. They used to be one of my favorite slayer task until i got 80 slayer and experienced nechryeal. By the way, there are only 2500 players who can kill abyssal demons... They have kinda good def so xp is not awesome, but loots are nice. So when someone gives advice on a monster practically anyone can kill I say: keep on the good work!