Hi Dave B
For your Brushed Motor set up.
In all cases you need to disconnect the red lead from one of the Esc's.
Pro's: You can control each motor separately if you use two channels on your Tx/Rx; The model will be able to turn in its own length; If one motor stops you can use the other motor to return to the side of the lake.
Con's: If you use a Y lead to connect both ESC's to one channel you will lose separate control and if the motors or props are not balanced one may run faster than the other; A dead motor will require recovery.
Pro's: Easy to set up;
Con's; the Esc will need to be rated at the max current for both motors; Similar problems with unbalanced motors or props.
Many systems offer mixing facilities allowing you to run say two motors on separate ESC's connected to two channels. You can then use one stick as a master channel and the other as a slave. This avoids using tank steering.
You can buy external attachments that will allow you to use one channel to control two ESC's and also link in the rudder control to reduce the inner prop speed on turns.
I have used all variants and all work but for a tug I prefer tank steering as this gives me absolute control in all circumstances.
For fast navy craft I prefer using a mixer on my Tx and I also use on my large passenger liners as the electronics manage the control far better than my ageing brain cells.
As an ex flyer I am not phased by using multiple Tx controls but accept that it is not for everyone.
Finally before anyone asks you can not connect two Brushless ESC's to one channel.
Hope this helps