I'd say they're even at lots of things, with Myhill's distribution being slightly better.
However, the thing which swings it for Foster is that he'll come off his line, unlike Myhill who seems rooted there and has been caught out a few times. Myhill is a nice number 2 to have, but Foster is better in my view.
That being said, big injuries can and do take it out of players so it will be interesting to see if Foster shows any decline after such a big injury.