Silicone rubber is more durable than EVA foam. It's also more expensive than EVA foam.
Both
can be cut easily with an X-Acto knife or a sharp pair of scissors.
Both have a tendency to rapidly dull whatever blade is cutting them.
EVA
foam is easy to paint, but tends to create creases and lasting marks in
the paint when the armor piece is bent repeatedly. Silicone rubber is
more difficult to paint, but won't create creases or marks in the paint
once it's set.
EVA foam is best adhered
using contact cement. Silicone rubber is best adhered using a silicone
bonding agent. The silicone adhesive is slightly more expensive than the
contact cement.
In summary, when it comes to
making flexible armor pieces, silicone rubber is a more expensive and
more durable option than EVA foam. The two materials are about equal to
work with in terms of difficulty.