yes, there is a difference
a secret, in most cases is something which is shared mostly through trust . "if I tell you something will you keep it a secret"
if you say "yes" then you're bound by the secrets act. the unwritten code of secrecy. it supersedes everything: friendships, family etc etc. there's no grey area
on the other hand a lie is a break/ breech of trust.
[that said in some situations exposing a secret might be the best/ right thing to do, but you'd still be breaking the secrecy act
in what situation do you think it would be the right thing to do to break a secrecy pact