What's a better investment? Buying an ASIC-based mining rig, or buying bitcoin itself? Seems like some miners are saying they would have made more money by simply buying and holding Bitcoin, rather than mining it. Is that likely to be the case going forward? I know I'm asking for speculation -- but, if one is working under the bullish assumption that BTC will gain in popularity and more people will start using it, is it a better bet to buy and hold than to invest in mining equipment?
Investing in expensive mining equipment hedges a bet that the return on investment, in the form of Bitcoin, will eventually pay off the initial investment and continue paying a return for some time before becoming obsolete (like CPU mining has and GPU mining shortly will) or breaking down. It may be possible operate this as a business, writing off expenses while selling generated Bitcoin for a profit. This is all based on an assumption that this mining system may eventually be profitable. It's safe to assume that it will be once running, but, like any dividend play, it's a long term investment. Unlike dividend plays, the return will likely only decrease over time.

By buying Bitcoin itself, one participates in the economy. While Bitcoin supporters would hope that one would not hold on to Bitcoin as an investment, but rather spend it in order to further the economy, it is possible to still make a return on investment if one's goal is to earn a return in government issued currency.

Consider a $1,200 investment in a mining setup versus a $1,200 investment in Bitcoin itself. 

The former is a long term play, slowing building up to profitability through the course of months or years. Something may happen that causes the system to fail and halt returns.

The latter is a more liquid play, where one can sell the Bitcoin at a profit (or loss) short-term or long-term, or exchange Bitcoin for goods and services, thereby furthering the economy.

It comes down to investment style. Does one fancy themselves a miner or a jeweler?