Statistically if you had enough hashing power to more or less assure yourself a solved block before difficulty change then you could potentially come out even or ahead. Otherwise in an accelerating difficulty frame solo mining will fall behind pooled mining for most people. Luck is, of course, luck.
This is a bogus argument.
Consider: You give me a dollar. I roll a six-sided die. If it comes up '1', I give you $1,000. You only get to play once.
Is this a good deal? By your reasoning, it's not. Most people who take the deal will come out behind $1.