But they are not as easy to use.

Yes lamentably to greater security less usability

I guess it all boils down to accessibility. Let's say Bitcoin becomes obsolete over night and you have your 400k in an encrypted walllet.dat file in a safety box somewhere, and no Bitcoin client capable of using wallet.dat files on your computer.

Of course if you have a .dat saved but you do not have the node updated for an emergency,
you are in a disadvantaged position which you should avoid .

You'll be in a hurry trying to first get to the backup, then wait for Bitcoin to rebuild the blockchain from scratch which can take anywhere from 4 days to 2 weeks depending on things. (Been there done that.),

Yep, I updated the BTC client days ago, in a laptop that I have as a wallet "offline" and it was about ~ 150GB, and it took about 3 weeks to update

By the time you're done, the price has dipped below 20 bucks and you're left with nothing.

I have a real case of a friend who had 7 million PandaCoin saved and the node was outdated, when I finished the update the price had dropped by 90%

So, the moral, you should always have an updated node for emergencies

But you are right, if the web page is down, it's pretty much the same issue. (Although like I said, the python commandline client does work without the web page.)

Yes, the commandline python gives some reassurance that you will have a way to access the wallet, but I do not trust third-party solutions I have seen many companies simply close their doors and the clients run out of support

Well at least for this case of saving your cryptos, the cryptos usually stored for years and one never knows what would happen

:P