Should Litecoin be the new crypto for currency, and Bitcoin exist as just a store of value?
Excellent question.
Bitcoin is only a store of value whilst people think it has a value, which is because it can or 'will' be usable to buy things.
If it's ever proven that it doesn't work for commerce (and I believe it doesn't) then it's value will be fraction of what it is now.
Well how long will it take to prove that it doesn't work for commerce?? Surely there has been plenty of time already for something like that to be proved true or false.
Bitcoin has value because it is set to become the world's reserve currency replacing the USD and also for global trade replacing SWIFT. That is where it is headed. The signs are clear from the adoption of Bitcoin in China. They've been looking for a way out of the USD trap they are currently in and this is it.
It might take decades. For a currency to be used as a unit of account in commerce both parties have to be willing to use it. Not just some mechant and some customer but the specific customer looking to use a specific merchant. For an individual to use a currency as a store of value they just need to believe that SOMEONE, anyone will accept it in the future. That is somewhat simplified but you can see the network effect requires for direct commerce are much higher than for a store of value.
Imagine a hypothetical store.
Does the store accept Bitcoins? No? Then no Bitcoin commerce is possible.
If the store accepts Bitcoins does the customer have Bitcoins to spend? No? Then no Bitcoin commerce is possible.
However if you believe that Bitcoin will be increasingly used as a store of value then that means in the example above the second requirement is more likely to be fulfilled in the future even if it isn't today. 100K Bitcoin holders means 100K potential customers. 1B Bitcoin holders means 1B potential customers. If adoption as a store of wealth continues to grow (not just value of the currency by the number of individuals holding it). More currency holders means it is more likely merchants will accept it as payment to gain access to those currency holders.
Imagine I am a merchant that makes widgets and all my competitors make widgets. At the current time none of us accept bitcoins as payment. If someone has wealth stored in bitcoins and wants a widget (lets assume these widgets are expensive) they need to trade it for local currency and buy indirectly. This means they face additional time, cost, and risk. It would be much easier for this bitcoin holder if at least one widget maker accepts bitcoins. If I accept bitcoins then I can gain an advantage over competitors even if my prices are marginally higher (as long as bitcoin holding customers see value in a direct transactions). If you believe in free markets and economic competition then the end game is that eventually there will be large enough critical mass of potential customers that at least one widget maker will accept bitcoins to tap that market.
A currency can be used as a store of wealth or a unit in transactions. The store of wealth use requires less of a network effect so it will grow quicker but baring some failure of the system that will boost the growth as a transaction unit use as well. It however will take longer and require more potential customers holding the currency. We have seen this effect somewhat already. The earliest holders of the currency were miners so products and services offered for bitcoins that met that demographic were more successful than ones which didn't. Think used computer parts vs cosmetics.