K.R.
Pretty cool website to compare and research seats--
http://www.elitecarseats.com/user/add_item_to_comparison.cmd
According to the specs, the Recaro is a little taller and much wider, so I guess that means if you think your boy will need the room, that can be a great benefit.
My mom just bought a Recaro Como for her car for my daughter's use and it is very cushy and looks great for side impact protection. The foam is thick all around. My 13 month old liked sitting in it (even though it was still in the living room!). I don't know what the differences are btwn Como and Signo, but my mom got a phenomenal deal on hers b/c they are closing out that model.