Some comments from @sipa in #12702.

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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, ...).

std::vector<std::string> keys = sendTo.getKeys();
    for (const std::string& name_ : keys) {
        CTxDestination dest = DecodeDestination(name_);
        if (!IsValidDestination(dest)) {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, std::string("Invalid Bitcoin address: ") + name_);
        }
        if (destinations.count(dest)) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated address: ") + name_);
        }
        destinations.insert(dest);
        CScript scriptPubKey = GetScriptForDestination(dest);
        CAmount nAmount = AmountFromValue(sendTo[name_]);
        if (nAmount <= 0)
            throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
        totalAmount += nAmount;
        bool fSubtractFeeFromAmount = false;
        for (unsigned int idx = 0; idx < subtractFeeFromAmount.size(); idx++) {
            const UniValue& addr = subtractFeeFromAmount[idx];
            if (addr.get_str() == name_)
                fSubtractFeeFromAmount = true;
        }
        CRecipient recipient = {scriptPubKey, nAmount, fSubtractFeeFromAmount};
        vecSend.push_back(recipient);
    }
    EnsureWalletIsUnlocked(pwallet);
    
    if (totalAmount > pwallet->GetLegacyBalance(ISMINE_SPENDABLE, nMinDepth)) {
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Wallet has insufficient funds");
    }