I can't say one or the other globally. It is very much game dependent for me. There are open worlds that are just wonderful and it's joy to play them and there are others whose world is empty and useless and that sucks.
One of the best executed open wolrds is old Gothic IMO (Gothic 2 is great too). Sure it's probably ugly and bland by today standards, but the world is absolutely amazing. It's completely open from the start, but player is so weak it is probably good idea to play semi-linear at the beginning. But nothing (except for tough enemies) stops you from exploring whatever and whenever you want. And there are tons and tons of things to explore. Hidden cave with loot? Shortcut connecting two roads? Place with very rare alchemy ingredient at the end of narrow valley? Shadowbeast lair? There is so much love put in there I still have cravings to play it even though it's like quarter of century old game... Quite the same can be said for e.g. Morrowind which is another absolute gem from early 2000s.
But there are also open world games where open world either simply sucks or serves no purpose. I'd have to think about which games fall in there, because once it's like this I tend to uninstall and forget the title...