The great connector debate... lmao
This one ranks up there with the radio brand debate, where everyone will have their own preference ( me - Futaba is best, Tony - Spectrum/JR ... lmao ). In the end, there is no best... there is what works for you the best. I'll avoid the "which is best" debate and just try to cover a bit about the 4 mentioned already that fall into the 40-60a rated load arena...
Of the 4 brands mentioned... there are two types... The Deans, EC3 and XT60 are solder types and Anderson Power Poles ( APP ) use a crimp on connector. Technically speaking, a properly made solder connection is the most reliable and isn't affected by corrosion like a crimp connection... The downside ( if you will ) for a solder connection is that not everyone can consistently make them properly which can lead to poor or cold solder joints that can lead to failures. While a good crimp on ( like APP ) isn't as reliable in the long run as a properly made solder joint... the crimp connection can be made properly more consistently so a lot of companies ( including NASA in certain cases ) are using a crimp in some locations they previously had only used solder before.
Personally... I will go with a solder connection every time. There are a lot of times that a solder joint has to be used so no matter what, you will still need to learn how to properly solder at some point even if you choose to use a crimp connection on most of your battery connections... so I see little reason to purchase a good ( high dollar ) crimper AND also learn/know how to solder anyway...
Ok.. rated load capacity... this is actually a little more complex than it may seem.
The industry ratings on the connectors are for constant load scenarios... In other words, the connectors won't fail or overheat if they are used at their rated load setting constantly... In the RC hobby we seldom use the power systems at their highest load constantly, this actually gives us a little more leeway and in many situations we'll use a 40-60a rated connection reliably in situations where sometimes we are actually pulling up to or even over 100a.
Personally, I'm a sceptic first and I prefer to follow industry safety guidelines... I may push a 40-60a connection to 75-80a... but I feel very uncomfortable taking them up to 100a and over. The number of reports of people that use these connectors in 100a and over situations successfully is significant and I've actually have only heard of very few that have mentioned any failure... so I can't directly argue with them... I'll simply say that it isn't something I'd recommend and then let the user themselves decide without arguing the point with them.
Now... about the different connectors... Let's first take all of the clones out of the picture. There are many well made clones but there are also a lot of cheap ones that aren't well made so it makes it difficult to discuss the clones here... if you choose a clone, it will be up to you to do your own testing to see if it is a reliable one or not.
The Deans connector... first there is no actual industry rating placed on these by the WS Deans company. They ( rightfully ) claim that there are too many other factors, including the quality of the solder joint and type of wire etc, to actually place a rating on them straight up. The hobby itself will conservatively rate these at 40a and less conservatively at up to 60a. Using my "that looks about right" engineering ( lmao ) skills... I'd say the gauge and surface area of the connection looks like a 50a rating to me ( for whatever that is worth )... Like I mentioned, these have been used for years in power systems that go up to 100a for a long time, who am I to argue much with what others have reported.
Deans connectors are used by the majority in the rc hobby... this fact alone means a lot when choosing a connector. If you choose this one... more than likely you can loan or borrow a battery with others at the field if needed. This is my own connector of choice in applications that require up to 80a... for applications requiring up to or over 100a... I go with the EC5 connectors ( which I'm not discussing here at this time ).
The EC3 connector... This connectors is rated at 60a by Horizon and it is the connector I first chose and still have on a few batteries and planes ( I use adapters with my other Deans planes/batteries ). Like the Deans, many have used this in 100a and just over applications. Typically, most will say these are easier to take apart than the Deans but it hasn't been as widely adopted so the chances of sharing batteries is limited. This connector is the secondly most used connector behind the Deans which is used the most.
The XT60 is now starting to be used a lot because these were made by the Asian market as a cheaper alternative to the Deans and EC3's... While they are rated at 60a, that is close or even may be an over rated limit ( industry rating wise ). I've heard of a number of reports of these getting hot in 60a applications so I'd be sceptical in using them at higher amp loads. They are easily taken apart, but for me, they'd need to improve the plastic to handle the heat better before I'd consider using them. The problems I have with them isn't caused by the connector itself which is the same size as an EC3, it is with the plastic they use to hold the connector.
The APP 45 ( they have many different sized rated connectors ) are also starting to be a relatively popular connector. These are a quality product and because they use a crimper, they are often liked by those a bit timid about soldering. Everyone that uses them recommends using the recommended crimpers instead of the cheaper knockoffs that are available, they say they are worth every penny even though they are considered high priced. While I'm a die hard soldier fan, the industry and many users say this type of crimp connection almost rivals a good soldier joint and takes the question of it being a proper soldier joint out of the question... I haven't used these, but what I've read about them can't be ignored either... these make a good and reliable choice for those that would like to not deal with soldering.
