Advantage of doing research in theoretical high energy over other fields? I am undecided about the field I want to do my PhD in, in graduate school. I am asking because the applications that I am filling ask me to write the intended field of study. 
I found the people who do theoretical high energy physics are the best one able to describe physics and explain it at all levels, otherwise my choices are neutral. Since I am just a student and do not know the big picture of this field and other fields in physics, I want to ask what are the advantages and disadvantages of doing a PhD in theoretical high energy physics?
 A: 
I found the people who do theoretical high energy physics are the best one able to describe physics and explain it at all levels, otherwise my choices are neutral.

It is all well and good to go to graduate school and get a high level degree that will open up possibilities of work in industry  and industrial research.
The way you phrase your question tells me you are good in mathematics and understanding theoretical models and are wondering whether to go into an academic track pursuing theoretical research.
I think that for an academic research career one should be passionate about the subject chosen. One should pursue it because answering the questions that arise is important, emotionally important, and one cannot let go, similar to the passion an athlete has in pursuing olympic records.
For a career in high energy theoretical physics emotional commitment is even more important, because of the competition as somebody else commented.
I will tell you a story: I was fortunate to take part in a theoretical workshop, presenting experimental results, in Crete in the 1980's, where a lot of high level theorists including Feynman and t'Hooft were participating.
For light relief there was a walk down the Ravine of Samaria, a beautiful ravine with a small river running down it to the sea in the south. The fastest walkers took 4 hours to walk down. Feynman and a bunch of theorists took 8 hours, swimming in the river waters while all the time discussing problems of QCD theory, which was the current problem at the time.
It is also called a one track mind, the track being the theoretical problem of the time.
The moral of the story is that, even in lovely surroundings, with water playing and birds singing and nature calling, high energy theoretical physicists are obsessed/preoccupied with the problem at hand.
A: I am finishing my PhD in General Relativity / mathematical physics so I might be considered a freak by fellow physicists, but can tell you this. High Energy Physics goes nowhere now as String Theory fails to produce any measurable prediction in two decades. There is no progress in standard model too. Problems left in GR/math ph. are either very difficult or exotic. If I were you I'd choose a field as close to experiment as possible because standard theoretical physics is practically dead. Go for mathematical biology/condensed matter/quantum information/whatever. Unless you are a monk-type mathematical freak as I am, but then you wouldn't be asking this question in the first place ;)  
And do not worry - If you love physics you will be able to explain most phenomena regardless of what subdiscipline you choose - just keep curious over the years.
A: Hilariously, I think astrophysicists (the ones who do observation, not the theorists) are the ones who are most able to explain a wide range of physical topics. This suggests that it is extremely dependent on where you are, and who you sample. 
I'm a condensed matter theorist who works on biology. I chose condensed matter because in its abstract form it's about finding generalised ways to re-construct bigger scales from the smaller ones, which is going to become more and more important, since the Standard Model does a pretty good job of being sufficiently precise for almost all practical purposes. If you've never come across it, Phil Anderson's old essay "More is Different" is a read.
A: Statistical Mechanics is the future of Physics.  See the works of Roger Balian for some of the most exciting ideas around. 
See http://www.mth.kcl.ac.uk/~streater/balian.html
and http://www.academie-sciences.fr/academie/membre/Balian_Roger.htm
The main « problem » in Statistical Mechanics has been its robustness, i.e.,
the properties in the large of an assembly do not have a sensitive dependence on the microproperties of the constituents of the system.  But as some such parameter varies, suddenly the large-scale properties change approximately discontinuously or catastrophically.  The practical importance of metal fatigue and the theoretical interest of super-fluidity are both examples of this.
Meso-scopic properties will be at the forefront of nano-technology and many of the most important future developments of physics, so forget cosmology and elementary particles, think about the new kinds of statistical limits needed to study mesoscopy instead.
