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 (data.exists("timestamp")) {
        const UniValue& timestamp = data["timestamp"];
        if (timestamp.isNum()) {
            return timestamp.get_int64();
        } else if (timestamp.isStr() && timestamp.get_str() == "now") {
            return now;
        }
        throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Expected number or \"now\" timestamp value for key. got type %s", uvTypeName(timestamp.type())));
    }
    throw JSONRPCError(RPC_TYPE_ERROR, "Missing required timestamp field for key");
}
UniValue importmulti(const JSONRPCRequest& mainRequest)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(mainRequest);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, mainRequest.fHelp)) {
        return NullUniValue;
    }
    
    if (mainRequest.fHelp || mainRequest.params.size() < 1 || mainRequest.params.size() > 2)
        throw std::runtime_error(
            "importmulti \"requests\" ( \"options\" )\n\n"
            "Import addresses/scripts (with private or public keys, redeem script (P2SH)), rescanning all addresses in one-shot-only (rescan can be disabled via options). Requires a new wallet backup.\n\n"
            "Arguments:\n"
            "1. requests     (array, required) Data to be imported\n"
            "  [     (array of json objects)\n"
            "    {\n"
            "      \"scriptPubKey\": \"<script>\" | { \"address\":\"<address>\" }, (string / json, required) Type of scriptPubKey (string for script, json for address)\n"