I don't go there anymore. Very difficult. The Botanical Gardens have massive lines wrapping around the building and once you are inside, you are pushed through as fast as possible to keep the line moving. No chance to enjoy it and very crowded. Also a hassle to get there. Same goes for the Bronx display as it has grown in popularity. Gone are the days you can walk in on a Friday or Saturday night an hour before closing and have the place to yourself. Last time I attempted to get in there, it was a 3+ hour wait to see the trains, even with advanced tickets and being a member of the Friends of the NYBG.
I volunteered to do the National Christmas Tree Railroad this year and gave up a good chunk of my Thanksgiving weekend to volunteer to set it up. The Secret Service's rude and aggressive attitudes towards me and other volunteers, work conditions as a whole (fierce wind, soaking wet ground, mud, etc), general disorganization and chaos with no thank yous made me cancel the rest of my scheduled dates with the set up and operation of the display and I refuse to get involved with it again.
I understand Union Station has yet another new display. The O Gauge layout last year (a way lame layout at that) has been replaced by the old Norwegian layout rebuilt into an old western US theme with LGB trains. I haven't seen it and don't really plan to go down there if I don't have to (I'm there enough already for my daily commute but never go to that area of the building).
Outside of National Capital Tracker displays at the College Park Aviation Museum and the B&O Railroad Museum and the WVMGRS display at Brookside Gardens in Wheaton, I don't go to any Christmas RR displays.