readme: explain the tradeoffs between using Mbed-TLS and OpenSSL. Recommend using -d use_openssl on !windows systems

Author: spytheman

README.md

@@ -289,6 +289,13 @@ V comes with a version of mbedtls, which should work on all systems. If you find
 use OpenSSL instead, you will need to make sure that it is installed on your system, then
 use the `-d use_openssl` switch when you compile.
 
+Note: Mbed-TLS is smaller and easier to install on windows too (V comes with it), but if you 
+write programs, that do lots of http requests to HTTPS/SSL servers, in most cases, it is *best*
+to compile with `-d use_openssl`, and do so on a system, where you do have OpenSSL installed
+(see below). Mbed-TLS is slower, and can have more issues, especially when you are doing parallel
+http requests to multiple hosts (for example in web scrapers, REST API clients, RSS readers, etc).
+On windows, it is better to run such programs in WSL2.
+
 To install OpenSSL on non-Windows systems:
 
 | System              | Installation command             |