There are taxi stands on the 7th Avenue side (pointing downtown) and the 8th Avenue side (pointing uptown). If the subway works for you, it’s better and cheaper. Either way, it’ll be a mad dash after the concert.
If it's a nice evening I would consider walking - the distance is not great and coming out of a concert there would be thousands of people on the street.
DH and I often walk from a broadway show home to the upper west side - almost 2 miles.
Thanks for all your replies as that gives me options. I've looked up the no 1 subway route that was suggested and it seems there's a station that would get me just round the corner to my hotel.