Hard to say, I haven't fitted a wood core door yet but heres my opinion. Hopefully someone who fits them can comment for you too.
Wood filled in theory is more secure. Having said that the foam ones are pretty secure anyway due to the GRP coating. I tried to break up an old fiberglass bath a few years ago and it was friggin solid, Spent a good few minutes going at it with a sledge hammer and couldn't even crack it so I ended up having to cut it to pieces.
You can have a google and watch some videos on youtube of how both doors stand upto attack but to be honest most burglars are going to just smash through the glass on a window somewhere out of site and not a front door.
The wood core doors will be heavier so may possibly require more adjustments over there lifetime.
In theory if water ever manged to get to the wood (there was a post here recently where there was a leak in around the glass unit on a composite door) the wood could swell up and possibly be unrepairable.
I have no preference either way and would be interested in other peoples comments too. These were just some worst case scenarios that popped into my head.
Thank you for the reply.
I have in the meantime done some Googling and you are correct, I was rally against the foam filled but after reading it appears these can be prone to contracting and expanding, thus, in extreme cases splitting in the door.
Just wanted hear what other people on here thought.