Is unusual (non power-of-two) RSA key size more secure? On this blog https://blog.josefsson.org/2014/06/23/offline-gnupg-master-key-and-subkeys-on-yubikey-neo-smartcard/ there is a following sentence


  Generate master key
  
  Below I will use a 3744 bit RSA key, where the key size is selected based on the assumption that people will focus efforts to crack RSA keys on the usual power-of-two key sizes.


But that leaves me to wonder: do unusual key sizes really pose a disadvantage to a potential attacker? After all, couldn't he just get a key size from a public key?
From this answer: 


  The difficulty of factoring (thus, as far as we know, the security of RSA in the absence of side-channel and padding attacks) grows smoothly with $n$. 


So, if factoring is the method of choice for breaking RSA, it doesn't seem like it really helps.