The primary thing to note is that with long term keys (the way RSA is generally used, ie: with GPG the way it is usually used) if Alice has her private key compromised, all intercepted ciphertexts ever sent to her that were encrypted with that private keys corresponding public key can be decrypted. The way that (DH / ECDH) is usually used (ie: Tor, OTR), intercepted ciphertexts become impossible to decrypt with traditional (non-quantum) computing power as soon as the private keys are erased, which happens every time a new message is sent.