The IOTA java script library's getNewAddress function has a security parameter which can take the values 1, 2, or 3. Each value will generate a different address with the same seed - what's the difference?
What makes the address using security level 3 more secure than using 1? Why not always use 3 if it's more secure?
The security level affects two things:
How hard it is to brute force a signature for a key (or how hard it is to brute force a message that a given signature can be used to sign). This is mostly relevant if some parts of the key have already leaked (e.g. because of address reuse) or if you have a particularly powerful adversary (against normal advisories, every security level should be secure enough)
How big the actual signatures are. Level 3 signatures will need 3 transactions' space, so in a typical bundle you will have to add 2 extra transactions to store the other 2 parts of the signature. Therefore using Level 3 signatures requires more PoW and sending more transactions when spending from such an address.
"A security level determines the number of rounds for hashing, which means that a single seed can have 3 different accounts." Source: https://domschiener.gitbooks.io/iota-guide/content/chapter1/seeds-private-keys-and-addresses.html
Of course it is more secure to use security level 3 and it is also advised: "Only use 243-trits (level: 3 - quantum proof) security for addresses" (https://domschiener.gitbooks.io/iota-guide/content/exchange-guidelines/important-principles.html)
I hope this helps answering your questions.
