It's not something I know a lot about (I'm more interested in synthesised sounds!) but I believe you can create pretty impressive emulations of physical instruments using techniques like physical modelling. Not sure if it's comparable to a well recorded sample though.

I believe Audio Modelling are one of the leaders in this field: https://audiomodeling.com/

In terms of harder/easier... I'd guess it's a lot harder to code, but easier in terms of not having to sample thousands of different articulations for each instrument! Judging by the huge selection of sampled physical instruments and the small amount of synthesised ones, I guess overall harder. Would be interesting to hear from someone who knows more though!