You may be interested in the post at http://giantcod.co.uk/forum/viewtopic.php?f=121&t=1486&p=6204&hilit=connector rated#p6204. 😀
This gives good test details on several different connectors. Personally I use Deans connectors. All bought from China and never had a problem. Could be the Fly-Boys don't check their set up correctly and are using too many watts! 😓

Thanks to contributors above.
I have since measured the sockets and it seems that gold 4 mm may be best - will let you know after purchase and fitting.

The suggestion about soldering is correct every connection is another loss (I squared R watts).
I should mention that I taught electronics and am a Chartered Electronic and Radio Engineer (The IERE did not make any more after 1988 !).

Forgot to mention, Ive never seen 3mm connectors, 2mm, 3.5mm, 4mm. 5mm and evn 6mm but not 3mm.

I only use EC type connectors and replace the usual Tamiya ones with these. EC3 is the most common and are available from Componentshop who provide an excellent service. They are basically 3.5mm gold connectors shrouded in a plastic sheath and are pretty much idiot proofed as the and - sides are clearly marked and uniquely shaped. Hope this helps

You could always cut the connectors off and use some reliable solder instead and reduce the number of connections that can loose power through. 👍
but remember to slide some heatshrink tube over one of the cables first before joining!

Component shop are pretty good for all things electrical.

Q1 Are you sure that 3mm connectors are actually made?
component shop 'only' list 2mm, 3.5mm and 4mm see
http://www.component-shop.co.uk/html/connectors.html

Q2 Google turns up NO 3mm connectors 👎

When you have decided which connectors to use - remember
1) The (male) plugs go on the motor cables and
2) The (female) sockets go on the ESC cables and
3) Make sure that the sockets are well shielded with heat
shrink tubing so that there can be no shorting out of the
ESC outputs either during connection or use.

Richard