Well i love bonuses because sometimes it is a good way to have some profit out of gambling. Many gamblers use bonuses and it is really good. The same as bonus, cashbacks not happens all the time so you cant take all what you have lost. Better to use these two to make your chance of having some profit increase.
How will bonus help you get more profit?? Technically the bonus you are getting you will have to use that money to gamble or else you
will have to forfeit those earnings as withdrawing bonus isn't allowed on most of the sites.
While if you see cashback it is best if you gamble frequently, and also it is better than bonus because you are allowed to withdraw those
money unlike bonus which you have to spend again. Cashback can also help you reduce the loss significantly or increase your profit.
Worst thing with cashback is that you need to lose in order to claim them. while bonuses though requires some insane stuff, can be redeem even if you have not bet yet. So basically both have their advantage and disadvantage if you think about the requirements needed before redeeming those stuff. Though using both if it is available in the Casino site is a better choice