wrk2 vs wrk, trying to make sense of the results and reasons

server

$ cat base/index.js 
var http = require('http');

http.createServer(function(req, res)
{
  res.end('ok');
}).listen(80);

wrk

$ wrk -s wrk_report.lua -t 1 -c 1 -d 1s http://target.host/test
Running 1s test @ http://target.host/test
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     1.31ms    3.41ms  30.45ms   93.30%
    Req/Sec     2.50k   818.27     3.48k    70.00%
  2494 requests in 1.00s, 245.99KB read
Requests/sec:   2489.23
Transfer/sec:    245.52KB
------------------------------
50%,247
75%,585
90%,2456
99%,19627
99.9%,29251
99.99%,30454

wrk2

$ wrk2 -s wrk_report.lua -R 1 -t 1 -c 1 -d 1s http://target.host/test
Running 1s test @ http://target.host/test
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    10.84ms    0.00us  10.84ms    0.00%
    Req/Sec       -nan      -nan   0.00      0.00%
  2 requests in 1.01s, 202.00B read
Requests/sec:      1.99
Transfer/sec:     200.75B
------------------------------
50%,10847
75%,10847
90%,10847
99%,10847
99.9%,10847
99.99%,10847