There's 2 train of thought.
1. Get hardware and pay it off ASAP to start earning some profit. Here, kH/s per $ matters.
2. Get as much hash as possible to hoard as many coins as possible, because they have a good chance of doubling, trippling, etc several months down the road. Here, the highest kH/s matters more.
#1 is less risky with lower expectations of profit.
#2 is similar to investing to buy coins outright, but not as risky because even if coin prices stagnate and don't rise, they will eventually recover the investment and start to make a profit.
I am #2, I am hoarding BTC and not selling.
It is far more profitable to buy and hold coins if you think they will double or more in value. If you pay anything for electricity and mine-and-hold, then you are basically converting your power bill into monthly installments of buying bitcoin anyway, so it's risky and possibly even riskier than buying-and-holding coins directly, contrary to what you said.
The only way mining is LESS risky than buy-and-holding coins directly is if you use some or all of the mining proceeds to pay for power or cash out immediately, or if you have free power (which is very rare). For anyone who pays for power, if you mine-and-sell-immediately that takes away most of the risk, but also means you have a lot fewer coins that benefit from price rises, too, so you lose a lot of potential upside. If prices go to zero, a mine-and-holder may lose MORE than a buy-and-hold-coins-directly person because of all those power bills. In general, if you think prices for cryptocurrency will increase more than ~40%, and you pay average USA electricity rates, it's better to buy-and-hold coins directly. A little bit goes a long way, since this strategy has been 10 to 20 times more profitable than "mine and hold" and way, way, way more than 20 times as profitable as "mine and sell just enough immediately to cover power bills," and even more profitable than that vs. "mine and sell everything immediately."
If prices go to zero, miners have to deal with depreciated hardware (used 7950s would be worth less than half their going rate now, for instance) and all those power bills. Buy and holders can't lose more than they put in, and get all of their investment immediately rather than having to deal with decreasing trickle of coins over time as mining difficulty goes up.
It will not matter, what the BTC asics taught us is that new crypto coins will rise using new algorithms that ASICs cannot touch, and it will catch on fast due to all the GPUs out there.
Likewise, early adopters of ASICs will be filthy rich, but late comers will have a tough time.
@Torn Mind, it is not hard, just take most GPU design and remove all the rendering and output functions.
There is only room for about 2 major cryptocoins which derive their value solely from network effects (the more people who use them, the more valuable they get), just like Facebook and Google+ dominate social networks. Similarly, if you invest in precious metals, you know that gold and silver dominate.
Since there is only room for 2 cryptocurrencies and we already have them (Bitcoin BTC and Litecoin LTC), the only way a third currency becomes viable is if it kills bitcoin and/or litecoin to make room for itself. Whatever kills BTC/LTC, it has to be a lot better than BTC/LTC. Merely copycatting BTC will not work. Thus whatever kills BTC/LTC will likely NOT be yet another Proof of Work coin like BTC/LTC. It will likely be radically different such as a Proof of Stake coin which does not require "mining" for "block rewards" at all.
Even if somehow a third PoW "mineable" coin emerges to kill BTC/LTC, there is no guarantee that it will work as well on current cards. As someone said recently in this thread, scrypt-jane apparently works better on NV GPUs. So if a scrypt-jane PoW coin kills BTC and/or LTC, you will see a massive fall in AMD GPU prices and a massive rise in NV GPU prices.
Like I said though, it's way more likely that a Proof of Stake (PoS) coin emerges instead of another "mineable" coin. This is because the world does not need yet another bitcoin clone. It needs something that gives bitcoin-like advantages (or more) and yet fixes bitcoin's drawbacks like blockchain bloat and "mining" which wastes a lot of energy. Something radically different. And that something is unlikely to be mineable by CPUs, GPUs, ASICs, or anything else, because the entire concept of mining for block rewards will be done away with as it is not necessary to ensure security.