It appears that the OP did mention 3rd Rail in his post and I too would cast a vote for the striking NYC H10a especially in green this year 2024
I don't own one but have acquired several 'new to me' steamers of older vintage from MTH, Lionel, and Williams AND a 3rd Rail AT&SF Warbonnet E6 that is one of the best in it's class as well.
Lionel's SOUTHERN PS4 1403 is a real beauty also in green, both a Legacy and a Premiere Dreyfus behind the Santa Fe E6 below, and although not a locomotive, the 3rd Rail NYC observation is a real jewel and seldom seen. Williams produced a beautiful rendition of the PRR T1 that I have been looking for
Personally, my 'Engine of the Year' would be a toss-up among these posted here that were acquired in 2024.