With the cards as they are at the moment, I'd say Courtois is going to be playing in a more settled team and more organized defensively, at least at first. Our defence is still experimenting a new system, has had some important players leaving and is still pretty young. Playing behind a settled defence is an important factor for a GK, imagine our Dave behind the defensive unit Van der Sar used to have.
Even though Dave had a good season last year, it wasn't documented at all because our team looked a mess and we conceeded stupid goals (for which he wasn't at fault). He made one blunder whole season (COC against Sunderland after which he did tremendously in the kick out session, let down by our players incompetent penalties) and had a pretty stellar individual record apart from that, but it won't especially be remembered.
What I'm trying to say is that for a big team, the way the GK is judged is also due to where the team finishes and the overall impression of solidity it's given. It's not ALL in his hands, imo.