Adding my thoughts in, i'll mostly be echoing what's been said before. You shouldn't think of particle physics being altogether more esoteric - with molecular biology it would possibly be easier to explain to the layman why your studies are of more 'practical value', but is that how you want your future to be focussed? I have a friend doing a PhD in a particle physics group, who's focussed on the side of designing particle physics detectors - this has some very interesting 'real world' applications - for instance designing new types of imaging devices will improve things like cameras etc.
What it comes down to, for me, is picking something you will enjoy. No-one else can reasonably answer that question for you - if you investigate and have questions about specific things in those fields then I'm sure people will be glad to help out.