One reason would be that Monero has never reduced its rate of supply, because we stuck with the social contract even when the supply was a bit high for the market (causing dumping), and big investors wanted it cut. Darkcoin/dash did make cuts, as I understand it. Monero may have been originally designed with a somewhat faster supply curve, I don't know the details, but in any case that is somewhat irrelevant given that the darkcoin/dash supply curve has been changed multiple times.
There are better threads for this discussion though, such as
this one so feel free to join over there if you are actually interested. Other than correcting incorrect information, I never post about Monero here.
Here's what an independent review says about the Monero supply curve (click through to see an analysis of the entire blockchain showing everything is as it should be:
On one hand, a 4 year plan to produce 85% of the currency is waaaay better than 90% of the coins on this investigation. In comparison to bitcoin, we see that from its inception from January of 2009 to today, May of 2014 (roughly 5.5 years), bitcoin has produced around 60% of its expected coin totals 163). In that sense, Monero isn't too much of a divergence.
There are no instantmines or premines in Monero. The smooth block subsidy scheme could be a little bit more tapered towards a slower distribution than it is, but ultimately this coin passes the smell test.
Highly inflationary altcoin curves create a hooking addiction, where you must constantly throw more money to bring yourself to a better cost-average price, as the supply inflates and price is pressured to go down.
Most investors don't have the pockets to chase their losses all the time, neither are they willing to constantly feed their investment to get to a lower and lower price / cost-averaging their way. So those who don't have the pockets lose out, and those who do chase the investment (kind of like gambling where you are chasing your losses), get a lot of coins and an unexpected size of investment on their part (they wanted to go with an X amount of BTCs and ended up doing 5-10X).
One must admit that there is a "hooking the investor and get tons of his BTCs" element in this type of emission scheme. Fairness, in this context, is problematic because the regular guy can't simply buy 10 coins and expect ROI when the market is flooded with new coins. So, in a sense, only the deep-pocketed whales can gain - and even them might lose quite a few if they are invested from the start. You need a very weird investment strategy on when to enter, in order to not lose money.