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.
This is technically untrue. There is no "luck" in probability.
Can you try to count what is the possibility to get a bloct when solo and hashrate is 800MHash/s ?
Yes, you should be able to make a cumulative distribution function of this probability. Wikipedia it, find the formula, plug n' chug.