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I understand that a Bitcoin confirmation takes 10 minutes and I believe I understand the reasons behind that. Litecoin claims a transaction speed of 2.5 minutes. Potcoin claim it can be used for point of service transactions at a store with a confirmation speed of 40 seconds (Potcoin FAQ).
Why does Bitcoin take so much longer? Does Potcoin's claim of 40 seconds make the transaction less secure?
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Short answer, bitcoin was first. altcoins that came after thought that took too long and shortened it. Litecoin was one of the first ones that came after bitcoin and they made it 1/4 of the 10 minutes in bitcoin.
Long answer, there's a balance that each coin tries to make between block propagation and speed of confirmation. Satoshi was pretty conservative in choosing 10 minutes as there weren't any other digital currencies like bitcoin. Other coins have since tried shorter times, some as short as 10 seconds and have found that it works fine. There have been suggestions by former core devs that a hard fork could be executed in the future to shorten the confirmation time to 2.5 minutes or less for bitcoin.
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There are numerous considerations when tinkering block confirmation time as it would adversely affect Block Orphan rate if it is set too low and a lot of wasted computational effort if set too high. A high block orphan rate would lead to a lack of stability as confirmed transactions may end up in a state where it is unconfirmed, possible higher doublespend success rates, differentiating mining strategies to maximise block subsidy yields. As you can see, a shorter confirmation time would result in a whole lot of uncertainty, because a lot can happen when blocks are orphaned.
