Heavy shift knobs give a more confident shift and glide into place easier. But everyone is different. I like a heavy knob, I feel as though the trans grinds less and it 'falls' into gear easier.

Old knob on the left. Doesn't fit super well or look great, but it's nice for driving. Left is a "Nokya' knob off ebay. Cost me $12.99 shipped. It's really light, but it looks halfway decent.