Actually the latest mobile i5 and i7 are both Arrandale variants and support the AES New Instructions:

Core i5 2.53GHz: http://ark.intel.com/Product.aspx?id=43544 Core i7 2.66GHz: http://ark.intel.com/Product.aspx?id=43560

I think the only real difference is clock speed and that the i7 has an extra megabyte of cache.