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 (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    std::string label = LabelFromValue(request.params[1]);
    if (IsMine(*pwallet, dest)) {
        pwallet->SetAddressBook(dest, label, "receive");
    } else {
        pwallet->SetAddressBook(dest, label, "send");
    }
    return NullUniValue;
}
static CTransactionRef SendMoney(CWallet * const pwallet, const CTxDestination &address, CAmount nValue, bool fSubtractFeeFromAmount, const CCoinControl& coin_control, mapValue_t mapValue)
{
    CAmount curBalance = pwallet->GetBalance();
    
    if (nValue <= 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid amount");
    if (nValue > curBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
    if (pwallet->GetBroadcastTransactions() && !g_connman) {
        throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
    }
    
    CScript scriptPubKey = GetScriptForDestination(address);
    
    CReserveKey reservekey(pwallet);
    CAmount nFeeRequired;
    std::string strError;
    std::vector<CRecipient> vecSend;
    int nChangePosRet = -1;