Statistically the payoff is the same whether you solo or pool.
The difference is in the speed of payout.

Which would you prefer $1 a day for a year, or a lump amount of $365 a year from now. It's the same dollar amount.

Statistics do not guarantee anything. Soloing, you could hit the payoff in one day or have to wait three years+. Pooling evens this out to a very great degree.
So typically pooling is the best choice. However if you want to factor in luck then consider the following:

If you are a person who is known to be unlucky, do not do solo. Pooling is the way to go.
If you are a person who is known to have good luck, go solo. You will earn more as your above average payoffs will not be divided among others.
If you have no idea about your luck or are typical, go with pooled mining.