The difference is figurative v literal.
Not to a Catholic--and I'm talking about a REAL Catholic, not a "Kennedy" Catholic. The belief is that the Eucharist is the literal body and blood of Christ.
See:
http://www.catholic.com/library/Christ_in_the_Eucharist.asp
It explains the argument between the literal and figurative view of Christ being in the Eucharist, and rightly identifies it as a point of attack by what they are calling "fundamentalists".