Just to add to this- in a recent interview I was asked both. For why law I focused more on what had motivated me to do a law degree e.g. A level choice, career prospects, found it interesting etc, and then I also mentioned that becoming a solicitor was of interest to me as I felt it aligned with my skill set and I wanted a job that was client facing. Then for why commercial law I focused more on the type of work (e.g. it being international in many cases), the clients, and then also that I had an interest in commercial things in general from previous work experience etcinterview! more so in the context of if i get asked both, not sure how i would differentiate them.
I am by no means a professional lol but I did get the vac scheme so they must of thought this was ok hahah