speaking of difficulty --- is it a sure bet - cast in stone that btc difficulty will go up as advertised everywhere?
is that cast in stone?
if so - I keep wondering why people are investing $6k in 2 TH/s rigs that won;t be delivered until next month - I don't get the logic - or lack thereof...
thanks
Difficulty changes are not cast in stone, but recent difficulty adjustments are probably the best estimate you can make on what at least the next few adjustments might look like. You're right to wonder about the possibility of the RoI of current ASIC purchases with difficulty increases, but you also have to factor in future prices of BTC. If someone feels like the future of BTC is strong, than they may feel like future price increases will offset the difficulty increases.
To comment on your original question, I think you also have to look at WHY a given coin is at the top of coinwarz, coinchoose, or similar sites? I have seen coins that, after researching them, are almost completely dead, yet they show up at the top of those lists. In those cases I think you have to also ask yourself why they are at the top at that point? I usually assume a short-term pump only because a pre-mine holder wants the coin at the top of the list to gain interest so they can dump their holdings. What is the trade volume, what's the difficulty, and if there are not pools, which is often the case with these low-difficulty coins, are you want to deal with solo-mining it..?