ECC cards are thought to offer a compelling alternative to those based on the RSA cryptosystem.  In theory, smaller (i.e. fewer bits) ECC keys can achieve the same level of security as larger RSA keys.  Fewer bits typically implies that the required mathematical operations can be completed with less processing power, which is desirable in an embedded device such as a smart card – and especially so for contactless cards.  Fewer bits also implies a reduced storage footprint, although the difference is sufficiently few bytes that it doesn’t seem to be much of a concern these days.