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, ...).

if (!request.params[2].isNull())
        fRescan = request.params[2].get_bool();
    if (fRescan && fPruneMode)
        throw JSONRPCError(RPC_WALLET_ERROR, "Rescan is disabled in pruned mode");
    WalletRescanReserver reserver(pwallet);
    if (fRescan && !reserver.reserve()) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
    }
    if (!IsHex(request.params[0].get_str()))
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey must be a hex string");
    std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
    CPubKey pubKey(data.begin(), data.end());
    if (!pubKey.IsFullyValid())
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey is not a valid public key");
    {
        LOCK2(cs_main, pwallet->cs_wallet);
        for (const auto& dest : GetAllDestinationsForKey(pubKey)) {
            ImportAddress(pwallet, dest, strLabel);
        }
        ImportScript(pwallet, GetScriptForRawPubKey(pubKey), strLabel, false);
        pwallet->LearnAllRelatedScripts(pubKey);
    }
    if (fRescan)
    {
        RescanWallet(*pwallet, reserver);
        pwallet->ReacceptWalletTransactions();
    }
    return NullUniValue;
}
UniValue importwallet(const JSONRPCRequest& request)