Some comments from @sipa in #12702.

___

Yes, I think `importmulti` is superior in every way, except:
* Slightly less convenient to use (it requires redundant information, as you have to explicitly state what you want to import, and then give the keys/... to enable that).
* ~Doesn't support P2SH-P2WPKH yet~. Added in #14454

The latter can be fixed by just adding support for that case. The former can be improved by adding 'default' cases (e.g. if you prove a WIF private key, it can permit omitting the address, ...).

"only backing up the seed itself, and must be backed up too (e.g. ensure you back up the whole dumpfile).\n"
            "\nArguments:\n"
            "1. \"filename\"    (string, required) The filename with path (either absolute or relative to bitcoind)\n"
            "\nResult:\n"
            "{                           (json object)\n"
            "  \"filename\" : {        (string) The filename with full absolute path\n"
            "}\n"
            "\nExamples:\n"
            + HelpExampleCli("dumpwallet", "\"test\"")
            + HelpExampleRpc("dumpwallet", "\"test\"")
        );
    LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    fs::path filepath = request.params[0].get_str();
    filepath = fs::absolute(filepath);
    /* Prevent arbitrary files from being overwritten. There have been reports
     * that users have overwritten wallet files this way:
     * https://github.com/bitcoin/bitcoin/issues/9934
     * It may also avoid other security issues.
     */
    if (fs::exists(filepath)) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, filepath.string() + " already exists. If you are sure this is what you want, move it out of the way first");
    }
    std::ofstream file;
    file.open(filepath.string().c_str());
    if (!file.is_open())
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
    std::map<CTxDestination, int64_t> mapKeyBirth;
    const std::map<CKeyID, int64_t>& mapKeyPool = pwallet->GetAllReserveKeys();
    pwallet->GetKeyBirthTimes(mapKeyBirth);