The Cal 240, which is used in both of these watches.
If you think that the 5712 may be a watch to wear every day, you're wrong:
The bezel is a scratch magnet.
As for the complications, of course they are very different.
I don't think that the fact that you use them very often or not is important.
When you buy a Chrono, do you often use it?
They both are very desirable watches, and personally, I love them both, but I have a preference for the WT.
Not that I travel a lot, but I love the concept of the WT.
So, at the end, your wirst should tell you which one to choose between these 2 very interesting watches.
It is up to you, and only you.
Best,
Nicolas