For everyday use, I think the straight boom is good, and the type of work you do may be the determining factor on what side to put it on. If you are working alongside a road often, you don't want to be in the road working.
For bigger jobs, I like the knuckle boom. It requires a bit more skill to use, but when fitted with a winch on the folding arm, it maintains the precision of a straight boom, with the added up and over ability.
I like the reach of the knuckle, and I have one that will pick about double of the straight booms common on service trucks, though I have seen straight booms that will lift as much. They are not common though.
The knuckle boom is more rugged, and can be side loaded more than normal. It can also push or pull large pins. I rarely use the winch on it, as I am usually lifting something heavy or awkward, so I just hook up direct and go. It is a heavier crane, and takes up more space.
Like most things in life, it is a trade off, and the kind of work you mainly do will be the determining factor.