As with most programming decisions, it depends on the circumstances.
If we wanted to check if a co-ordinate was within a 2D area, using one line might look better.
if (x>left) and (x<right) and (y>top) and (y<bottom)
print "It's within the boundary!"
endif
But if we had more complex conditions it could get very difficult to read.
I would tend to say that it's best to use as few IF's as possible but without involving too many different variables and making it too complicated. So I might write the 2D area check as:
if (x>left) and (x<right)
if (y>top) and (y<bottom)
print "It's within the boundary!"
endif
endif
By separating the X and Y axes we've made it a bit easier to follow. It really is down to personal preference though.
