Q: Just sitting after SLC exam, I am so confused between +2 and A Level. Is it true that if one wants to go abroad, A Level is better choice?

​This is not simple answer, but you may wish to pay attention to this answer. 
The myth is that if you study A Levels it’s easier to go get into colleges abroad. That is not the case at all and let me explain. If you get good grades in A Level for example 3 A's then yes, it would be easier. With the internationally renowned degree, every college will know that you are academically capable. But if you get 2 D's and an E, you are is worse off than getting 60% in Plus 2 because the colleges know that you are not academically capable. With a 60% in Plus 2, colleges would not really know how that measures up and your application will be reviewed with a benefit of doubt. 
In fact, I know lots of students, who have gotten full scholarships studying Plus 2 and lots of students who have not gotten into colleges abroad even though they have studied A Levels.  Does A Level help?  Yes, definitely, if you get good grades.  If you get bad grades, it can hurt.  If you are very sure you can do well in A Level, and yet you want to go abroad, you may be better off with a +2.
Yet, this is not a simple answer.  There is one more thing to consider. That is the study-culture.  Having said that, A Level is a superior program to Plus 2. With constantly updating syllabus, curriculum dealing with current world problems, the rigor involved to get you to think critically, A level does prepare you better for higher education. But an A Level does cost twice as much or sometimes much more in certain colleges in Nepal, than for Plus 2 program.  Let us say that two people get into a foreign college with equivalent grade, say Ramesh with D average in A Level and Divya with a 55% in +2.  Who is better off? Ramesh would have had exposure to international study culture, while Divya would not.  Ramesh is more likely to succeed in that case. 
So, if you ask – does A Level help in study abroad?  The answer is yes.  If you as – is A Level an advantage to go abroad?  The likely answer is a ‘no’ unless you are likely to get top grades.
According to KesharKhulal, Principal at Budhanilkantha School, "Plus 2 is the best options for students in Nepal, but A Level is better if you can afford it."