as someone who studied a BTEC take my advice and stay well clear of it unless you are looking at engineering and are doing an engineering based BTEC. Anything else and do your A-levels
however, that said, even for engineering A-levels are a beter option.
Basically I found with BTECs is that they are not in anyway hard but are not easy at the same time. They basically require you to spend a lot of time right the way through the year researching for coursework or actually writing up the coursework. A-levels on the other hand require you to pay attention in class throughout the year and put the work in when the exams approach. For example:
if someone was to show a graph of students' effort throughout the year it may look like this:
A-level student -
works at 40-50% of full effort from September to mid/late-November
works at 80-100% of full effort from November - Winter tests
works at 40-50% of full effort from January to mid/late-March or Easter
works at 80-100% of full effort from late March - Summer tests
BTEC Student -
works at 60-70% of full effort from September - June
So as you see, BTEC needs a consistant work rate throughout the year, A-levels students tend to do the required school work then hit a sudden spike in extra study when approaching the exam period.
Of course some BTEC students do nothing all year and fail (keep in mind these are usually the ones too cool for school and go to college because they think they will get it easy and tend to fail or copy other peoples coursework and pass. And some work pretty hard the week before all their work is due and get a decent grade. The same for A-levels, so will work consistantly at a high rate and do very well, others will do nothing and fail.
But take my advice and do A-levels, or even better a cambridge pre-u or an IB which are better than A-levels.