Dean Marshall, manager at SBC Ramsey, had a 2025 with a jackplate a couple years ago. He added the jackplate for better rough water control and to improve shallow water handling. He did see some extra speed as well but the speed increase was never really the primary reason for the mod.
I did run the jackplate on both my 1825 & 2025 MX. Shallow water application was awesome for access to some of the hard to reach low water locations. Can you justify the cost or measure the benefits? Probably not for 95% of people.