Grasshopper and Contragrasshopper are certainly similar, and have the same Betza mobility (3.2 with magic number = .7, which would suggest a value around 1.5 pawns).
Since both will lose value rapidly as the board empties, I suspect their practical worth will usually just be a question of what you can trade them for. The Grasshopper (but probably not the Contragrasshopper) is very good at threatening undeveloped enemy pieces behind a pawn wall; replacing ANY of white's backrow pieces with a Grasshopper in an otherwise FIDE game allows a fork on turn 1. But without such a favorable opening (for example, if you start the pawns on ranks 3 and 6), I'm skeptical whether they are even as good as a Wazir or Ferz.