I'm a professional investor at a fund with billions of dollars and a lot of resources. Before I ever worked full-time I was a non-professional investor that invested in stocks directly and read a lot.

I'd say you should invest directly if:

• You find it fun (can be a great way to learn)
• You think you can have an edge over others in the market

Edges can come from many places -- better knowledge, better research, better analysis, better behavioural biases, etc.

Best way to figure out if you have an edge for a particular stock is to work out what the market thinks about the stock, what you think about the stock, what the differences are, and why you're right when others are wrong.