Yefi also has a Bitcoin Mechanics day, it seems. Pereira asking the questions again. At times I wish a merit source. Already asked for help, haven't I. Well whatever, both are legends already.
If yes, then I would still be paranoid of seed bruteforcing. There's something about Electrum that wouldn't allow me to sleep at night with any relevant amount of money in there.
The seed is just another way of representing a random 128-bit number. You'll have about as much luck bruteforcing that as a private key.
Keyword: a key. It would only take getting lucky once to get all of your money. With a wallet.dat you would need to go address by address. Who knows what those fuckers have in store when it comes to quantum computers within a couple of decades. Plus any mistakes on your part leading to key derivation exploits... yeah no thanks. Electrum seems like a bad idea for serious cold storaging.
The security of Bitcoin derives not from having many keys, but from having strong keys to begin with. The point at which randomly generated private keys become vulnerable to folk "getting lucky" we have a massive problem on our hands.
By the way, Bitcoin Core since like 0.13 I think has used deterministic wallets, so all your keys in wallet.dat are derived from a single master key now.
IOW, basically the same number of bits to crack - by sheer luck or quantum wizardry - as Electrum. If someone feels unsafe, they could divide the funds into multiple wallets, Core or Electrum or a mix (I'd keep it simple. Security by obscurity is bad anyway). Each wallet has its own master key or word sequence. The word seq can be seen as a master key in longer, human form.
Ideally, if you compress the sequence as hard as you can, the binary zip you are left with behaves much like a binary master key in Core style. The inverse process - from Core key to seed - isn't actually available that I know of, but it is entirely possible, easier if you're allowed some slack when "unzipping" - an extra word or something.