Arguments for Litecoin are fraudulent.
TL;DR: there’s no important difference between LTC and BTC and only one of them can win over another, because, other things being equal (which they are) people want to invest in the most liquid money: that is, with the biggest number of folks willing to hold it. LTC can’t be “silver to bitcoin’s gold”, because both LTC and BTC have exactly the same risks and costs. Either LTC wins over BTC, or BTC over LTC.
Litecoin/Bitcoin/Shitcoin are all long-term bets. I myself don’t speculate on daily basis, most of us bet for value of these things in the multi-year time frame. So let’s focus on that.
1) In long term security is not measured in “block interval time” or number of blocks. It’s measured in amount of money to be spent on double spending. Today hashrate of Bitcoin is many-many times more expensive than that of Litecoin. So one block confirmation in Litecoin is not just 4x less secure, but hundreds times less secure: you need smaller investment to fork the chain, than with BTC. So anyone who brings up security argument is lying to you.
2) Litecoin is not “faster” either. For the same level of security as in BTC, you have to wait hundred times longer (see #1). Instant transactions are the same and also less secure than in BTC: zero-conf, with less nodes and less connectivity between them to limit double-spend attempts. Anyone bragging about “LTC being faster” is a liar. It can only be slower due to less number of nodes and currently lower hashrate, not faster. LTC can only be faster if BTC is being abandoned and people switch to LTC.
3) “Scrypt protecting against concentration of power due to ASICs” is bullshit. If LTC wins over BTC, there will be ASICs and whole factories making chips and plugging them in on-site right away. Just like it will be with BTC or ShitCoin or else. Long-term LTC is either dead or is full of chinese ASICs, like BTC. Anyone arguing otherwise is a liar.
4) “Scrypt more secure than SHA256” is bullshit in the context of mining. If there’s a better optimization in SHA256, it’ll be like a better hardware. But this can equally happen to Salsa in Scrypt too. If the breakthrough is significant, all BTC stakeholders will vote for adjusting the protocol to fix the problem, not lose everything by panic selling. Huge price of BTC is a great motivator to find the weakness in double-round SHA256 and mine faster. Every day it doesn’t happen is only a practical proof it’s as good as it can be (just like Scrypt or whatever), everything else is unfounded FUD.
5) “More fair distribution of wealth” - this is unfounded FUD. For average Joe, LTC is less widely accepted, so its concentration, however “fair” it was, is still higher than in BTC. And who knows how much of early mined BTC are lost forever (we know that’s a lot) or were sold during 2011 bubble and slow price rundown the same year. I bet very few were sticking to their holdings that time and thus were taking huge risks “fairly”.
6) “Diversification” (based on all points above) - newbies who don’t know economics are made to think they diversify by investing in some altcoins. But the risks and costs are all the same for all coins. If Bitcoin is completely broken, most likely altcoins are broken for the very same reason. Otherwise, all Bitcoin holders will simply agree to upgrade the protocol. Especially so as Litecoin is on the same codebase.
The only real argument about LTC and BTC is that there’s no functional difference between them. LTC could only be 4+ times costlier to miners due to faster blocks and more “decentralization” of individual miners (slower connectivity, faster blocks => more orphans). If LTC was released before BTC and took off, everyone would be using LTC no problem. The only thing that matters here is liquidity, number of holders of money. If people are betting it is BTC with more hands, they send a signal to others about that by holding too. This moves all the “cryptoinvestments” into BTC in long term. If people see that LTC is gaining more hands, then everyone will converge on LTC. LTC and BTC cannot coexist together, it makes no economic sense both for miners (who want to invest 100% in the most valuable currency in long term) and for users (who want money only because it’s widely exchangable for many goods at any later dates).
Right now there’s a lot of excitement about Bitcoin and not many people understand economics. Some folks are lied to and “diversify” into altcoins, which gives them short-term bubble. But in years to come, when they see, that Bitcoin has bigger adoption, they’ll move their savings to BTC and then all altcoins will crash. Or for some mysterious reason BTC will not be viable and people jump to LTC en masse and abandon BTC.