I have been doing the plant electrician thing for a while now and settled on the best way to make splices for high amp connections for wiring up an electric motor, also building and repairing my own welding machines.
I wire up everything form little 1hp to 400 horse power motors that run at sustained high power for weeks at a time with out slowing down or stopping.
All use 480v 3 phase AC but same principals apply most are in wet corrosive environments, kind of like a vehicle driven on road in the rain and snow.
The little motors up to 10 horsepower just about always get wire nuts, no thrills there.
Anything over 25 horse can use several different kinds of hardware.
Your 3 go to methods for motor wiring are:
Polaris terminal blocks
Bolting terminal lug connectors together
Split bolt connectors.
Then covered with a few layers of rubber splicing tape and then standard vinyl electrical tape over that, unless the motor has a terminal board inside the pecker head.
My early favorite were Polaris connectors they were fast and easy to use. But they are expensive, can be $20 to $40 each depending on the size and type.
Before that I had mostly used terminal lug connectors bolted together.
Both can heat and cool and loosen over time. Both ring terminals and Polaris blocks use have connections that can loosen, over heat and develop higher resistance over time.
Polaris blocks and ring terminals have a tiny amount of surface area connection compared to just split bolting the wires together.
So, I would have to say the best hardware is just the simple, humble and cheap bronze split bolt connectors as long as you can keep the connection dry. You put the wire strands in direct contact with each other and crank them together with many hundreds of pounds of force. Nothing really beats that.
That's three 2 gauge and a 1 gauge wire connection that handles well over 1,000 amps on my home made spot welder and does not heat up.
But you can not use split bolt to go from copper to aluminum a Polaris connector should be used for that, if you use aluminum. (don't use aluminum)
This is an small alumiconn connector for 10 gauge wire, not a Polaris block but you get the idea.
If you need make multi wire connections (3 or more) that need to stay water tight the hands down choice is Polaris submersion and direct burial rated connectors, they are expensive but so worth it.
This one is about $30 to $40 just to make a single three 1 to 2 gauge wire splice. You simply remove the orange caps and jam the wire up in the prelubed sleeve. Then remove the black caps and crank down on the hex head set screws.
But on the smallest and largest AC motors and most DC motors seem to all use ring terminals on the motor.
That means some times you have to use ring terminals.
This is how I select good ring terminals.
Expensive ones are not always the best ones for the job.
Here are some 4 gauge ring terminals I have. Which one is better?
I bet you can tell which one is the cheap one.
The cheap connectors are a little more water resistant. The more expensive ones are usually built a little heavier.
To make the simple ring terminals more water resistant I crimp them and wrap some vinyl electrical tape around the copper terminal and wire insulation
You can also solder them after they are crimped or put some non-ox in the terminal before crimping. There are other ways such as liquid electrical tape to seal up the connection.