Hi, my brother is in the business of computers and hence can throw some light on this topic.
There was a time when buying assembled definitely made sense since the price difference betweem branded and assemble was significant. But now it is more sensible to go for a branded computer because of following reasons:
Price difference is not very significant from that of assemble computer
Quality Checks are more stringent on branded computers
After sales service is more professional and satisfactory for branded computers
Workmanship of branded computers is definitely better than assemble computers
Overall, you will be happier buying branded though initially you might have to shell out a bit more from your pocket
However, if you have a very close friend or a close relative who has very good knowledge of computers or is in business of computers, it might be still worthwhile to go for assembled computer. Please ensure that when I say’close’ friend or relative, I mean one who will do everything to get you the best. For example, though my brother is in business of computers he still asked me to go for branded one since he felt that he may not have time to come all the way to my house in case any support was needed.