Block Confirmation Speed - Bitcoin vs Litecoin vs Potcoin 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?
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.