I have EXTREMELY opposite kids.
My daughter [8 yrs old] thrives on chaos.
My son [3yrs old] thrives on organization and schedules.
I can't say anything about the vomitting thing. My son still doesn't know the proper place yet... And he's only gotten sick a handful of times. My daughter usually throws up [the first time] on her bedding, but she's upstairs and the bathroom is on the main floor. However, if she does get sick once, she has the trashcan next to her... And she'll make it in that if need be.
My daughter is my "stomach bug" kid. My son has an iron gut. He's my common cold or sinus infection kid. My daughter didn't have to have ANY antibiotic until she was almost 7, but pukes anytime she has allergies w/sinus drainage and had rotovirus @ only 17/18mos old. My son was on an antibiotic for an infection before his 2nd bday, but only puked twice so far.
They're polor-opposites as far as personality is concerned too. My son wants to do everything himself. My daughter wants everything done for her. He's laid back. She's ADHD. As newborns, my daughter didn't want to sleep... EVER and wanted constant stimulation. He slept great and was more than fine playing on the floor alone with a rattle. As toddlers, she was EASY. If someone told her, "Please don't do that/touch that, you could get hurt." She didn't and never attempted again. Him? OH BOY! It's the, "Let's see if it really does hurt me" challenge. Or, "How far can I really go with this..." She whines about everything. He just yells and gets mad.
We shall see in the next chapter of life. ☺