Benchmark

TCP is good enough when network is not heavy. But the experience is worse when packet is dropped for heavy network, for instance 10% packets dropped.

I've done some benchmark. There is a detail benchmark asio_kcp for heavy network, which indicates the latency of KCP is 1/3 of libenet:

worst network lag happen:
asio: 10:51.21
291  295   269   268   231   195   249   230   225   204

enet: 10:51.21
1563   1520    1470    1482    1438    1454    1412    1637    1588    1540

The detail data is here benchmark. Thanks the owner of asio_kcp zhangyuan to compare UDT, libenet and KCP:

ASIO-KCP has good performace in wifi and phone network(3G, 4G).
The kcp is the first choice for realtime pvp game.
The lag is less than 1 second when network lag happen. 3 times better than enet when lag happen.
The enet is a good choice if your game allow 2 second lag.
UDT is a bad idea. It always sink into badly situation of more than serval seconds lag. And the recovery is not expected.

And more:

enet has the problem of lack of doc. And it has lots of functions that you may intrest.
kcp's doc is chinese.
Good thing is the function detail which is writen in code is english. And you can use asio_kcp which is a good wrap.
The kcp is a simple thing. You will write more code if you want more feature.
UDT has a perfect doc. UDT may has more bug than others as I feeling.

I just compare the KCP with TCP/UDT, for I think libenet does not introduce modern transport techniques. The benchmark from owner of asio-kcp shows the difference of KCP/enet/UDT.