[MagicRat]

Try searching through the Chevrolet subforum; there are some threads on this subject.

Very generally, the automotive big blocks have a superior cylinder head design and usually have more displacement than the small blocks, so they produce more power.
There are much, much more small blocks around, so they small block is much cheaper.

That being said, it is quite easy to build and modify the correct kind of small block to make lots of power, often more than a big block.

This is where it gets complicated. Some small blocks are much better to build than others. You must do some research to make sure you get one that is worthwhile.

If money is no object, a well built big block is usually the best way to go, providing it will fit into your chassis.

Finally, people have written books on this subject because it is so complicated. There are hundreds of different ways these engines can be built so careful research is required before a decision is made.