Encryption is annoying. No it’s not!
Why do you even want to use a complex encryption algorithm instead of entering a password?
It’s much more secure (a 2048 RSA-key has 617 chars). But unlikely other encryption (PGP, etc.) it comes with comfort: You don’t have to enter the password after connecting to the server, but Putty authenticates at the server with your RSA key automatically.
howtoforge.de explains how to login to Linux-Systems with an RSA public-key.