Mining and trading do not contradict each other, but rather complement.
Its not about trading. The way ASICs are going, its better to spend money to buy the bitcoins rather than buy mining equipment and electricity to mine them.
People, who mined for some time usually buy equipment for mined coins. It is different, you investing nothing, but electricity cost. For those who want to enter mining better would be to buy bictoins and instead of just holding it, start trading. This summer people was making usd20K per month just buy trading on btc-e. If you holding bitcoins you gain only when bitcoins rate are going up. If you trading, you can make even more when bitcoins rate going down.
Fully agree with you. The OP though is entering the mining business, so IMO it doesn't make much sense to buy up equipment and start off.