I think the key point you make is that it depends more on the culture/environment than the policy. You can have a 5 week entitlement and still feel pressure not to take it. Or you might be able to take more than 5 weeks by going into "vacation debt" if your manager approves.

There's one distinction though: at least with a minimum entitlement you'll be compensated for unused vacation. (At least that's how it worked at a previous employer of mine.. it might even be the law?) So even if you feel pressure not to take it you'll get a nice payout. Not the case with "unlimited" vacation where nothing's on the books.