I'm noticing that the older 4216-4k costs more than the 5216-4ks2. From the specs, it looks like with one exception the 5216-4ks2 is equal or better. The exception is that the 4216-4k has 2 additional alarm inputs, and one additional output (6+3, vs 4+2). It doesn't make sense to me that the 4216-4k costs more, so I figure I'm missing something. Does anybody know what I'm missing?