I'm planning to get asus zenbook. Not sure if I should get one that is 500gb HDD with 32gb ssd or a 128gb ssd.
I'm planning to get asus zenbook ux3VD for the hdd storage or asus zenbook prime ux32A for ssd storage, but i5.
It depends on your needs. As long as the SSD is of good quality (what SSD is in the one laptop?) then it will MUCH better performance that is very noticeable. However if you absolutely NEED to store tons of files then you might need the HDD for more space. Also note don't try to cut it close either because you want to leave an SSD with at least 30% free at all times.
Don't worry about the SSD dying or anything because today's quality SSD's are no longer finicky or overly prone to breaking/give poor performance over time. Pretty much all of SSD's major problems have been resolved as long as you get a quality drive.