GetRsaPem returns the RSA key using PKCS1, whereas SaveRsaPemFile uses PKCS8. Both are correct, just slightly different internal formats.
Both GetRsaPem and SaveRsaPemFile are deprecated.
The GetRsaPem method is replaced by the GetPkcs1Pem and GetPkcs8Pem methods (given that PrivateKey may contain a non-RSA key).
Likewise, the SaveRsaPem file should be replaced by either SavePkcs1File or SavePkcs8File.