For me, I'd rather cease to exist in the first place because that means if I were never 'born' nor came into this world, I couldn't suffer at all. With that said, I'd rather CTB than to live a long life with suffering and all the ills that I face currently (and those to come in the future). This is because even if things do improve, they will once again go to shit in the future, it's a never ending cycle until death.
By CTB'ing I would prevent future suffering even if I miss out on potential pleasures. I don't see anything worthwhile in my late life to be worth all the suffering and even then, it is fleeting as life gets unbearable again. As someone who has lived over 29 years of his life on this planet, this world, I know enough about life to come to the conclusion. I have also pondered this for more than a decade.