Letusreason ministries agrees with my view that unleavened bread best shows Christ:
http://www.letusreason.org/biblexp184.htm
When something is used consistently and almost unanimously in Scripture the same way we must conclude , unless there is some obvious deviation of its consistent use that it is the same. This is true for symbols, which leaven is. In the Old Testament leaven is consistently used to represent sin, what is false and evil…In the New Testament, leaven was used to represent Pharisees false teaching, of the unbelief of the Sadducees by Christ (Mt 16:6-12; Mk 8:14-21).
We proclaim Christ was sinless by the elements we take that represent Him. Paul describes the unleavened bread as fulfilled in Christ 1 Cor. 5:7-8. The fact that Jesus held up matzah (unleavened bread) at the last Passover supper, saying “take and eat this is my body,” this bread was required to have no leaven in it, explaining he was without sin. The wafer was made with no leaven in it, because leaven is a symbol of sin.
If we are to take Jesus's words literally then to "take and eat this is my body" refers to unleavened bread. The disciples knew what this unleavened bread symbol meant - His body was sinless. Unfortunately, some people on this forum do not know what it means. Christ chose the type of bread to represent His body for a reason.