Personally, I think the drops on Guardians are a bit more intense than Tower of Terror was, but I have absolutely no scientific evidence to back that statement up. LOL. Just me being like, "WHOA!"
And it can absolutely cause motion sickness, if someone is prone to it in an rapid up/down sort of situation. (I don't get motion sickness, but I have felt a tiny bit queasy on Guardians before. Not enough for me to stop riding it though.)