[Kunzite]

That's exactly why I'd say "similar" is not quite the right word. They're both lenses, they're both of the same focal length and maximum aperture, they're both covering the same format, and they're both made by the same maker thus following a roughly similar styling.
But this goes without saying. "Similar" should be more than that... but, there isn't more.

There are some MTF charts and comparison with the old DA* here:
http://www.ricoh-imaging.co.jp/english/products/star_lens/special/sp_da16-50/