No I wouldn't say so, I know a lot of people who do both subjects and are doing fine.
Also I hear the legal part of the business syllabus is also learnt in legal studies so that a bonus.
Are you naturally inclined to enjoy either of those subjects? Both are heavy on the reading and rote learning hence it comes down to what you're good at.
For me, I struggled with memorising cases/etc and ended up dropping legal studies at the end of year 11... but ironically enough, when I did my business law (i.e. legal studies in uni - different to real law), I actually did really well in those subjects. *shrug*