yaks is only 5k to 10k less xp an hour than slayer? i always thought it was like 80k-100k xp? and yaks is easy to ask and such. thats why i use to do it and you dont need to worry about food. thats probably why most people train there.
slayer is better then almost all regular training spots, black masks and hexcrest are really useful in getting xp. i train defence on my tank using slayer. (level 90 def atm )