In terms of practical work in the BTEC it is very useful, and to clarify you wont be spending every lesson taking computers apart, that is something you have to do once in a unit called Computer Systems and it only makes up 1 out of 11 criteria for this unit, you will also have another 17 units of similar size where you will do a COMPLETE range of things including programming, software design, maths, computer architecture, operating systems, networks, databases, systems analysis, information systems, and a lot more depending on the modules chosen by the college
if you want a course with little practical work take A level Computing, however this isn't as good as the BTEC in my opinion, for example 2 areas where the practical and vocational element of the BTEC is really beneficial is in Programming and Networking, in A level you will just learn the theory whereas in BTEC you will also learn the theory and have do assignments to demonstrate this. with Networking we had 2 theory assignments and then we also had to put that theory into practical and design and set up a network using the colleges old hardware, we got hands on experience in server configuration and using Windows Server OS, we also set up a multi-player network game running across the network as a demo for an open evening. in Programming, A level is good in the sense that there is a lot of time dedicated to teaching whereas sin BTEC we were taught the principals and then for our assignments we were put into the scenario of working as Software Engineers, and had to develop a piece of software for a fictitious company, we had to follow a set development methodology and document the life cycle as it would have to be in industry, we had to do requirements analysis, model those requirements and produce good quality UML documentation for the software as well as extensive testing, user analysis and around a 4000 word evaluation, this practical experience in the BTEC is very useful if you want a career in the IT industry and has also prepared me wel for university, and i would highly recommend it, however if you want to follow a more theoretical path it would be worth taking A levels in Computing, Maths and one other, however the BTEC does also still have a substantial amount of theory involved with it
Hope this helps