After using dozens of these I can say:
1) Zero risk of melting plastic connector when soldering.
2) Very easy to solder.. a) Strip 1/8" of wire and tin it. b) Put EC3 in grip or drill a hole in a block to hold it. c) Heat EC3 with powerful soldering iron (I use 100w) d) Melt solder directly into "cup" on EC3 (only a little, about 1/2 full). e) While still applying heat slowly dip tinned wire into the cup. f) Remove heat an hold steady for a few seconds g) Snap into connector (polarity is clearly marked) h) Repeat for other connector.
3) These connectors will never come apart by accident.
4) EC3's would be very difficult to accidentally short out.
5) If you have a 5S or bigger battery consider an EC5

I was pretty much satisfied with the performance of the Deans connectors I had been primarily using since I got into RC about 1.5 years ago. I was not very satisfied with soldering them, though. The YouTube videos make it look super easy, and I have done okay with them sometimes, but other times I just can't seem to get it right--I wind up with a sloppy solder, I melt the connector, forgot the heat shrink, etc etc. Now, I know it was probably all because of my lack of skill or a cheap soldering iron or whatever. I'm not blaming Deans. They are without a doubt the most popular connector and are a quality product, but maybe they are not for everyone.

So I decided to try these--even though I once complained to Horizon that I wish they would not use proprietary connectors! I am so glad I did. I soldered a battery and ESC in just a few minutes on the first try--with my poor skills and poor soldering iron!

I'm sold on these now and will use EC5's when I move to larger stuff. It also helps that my local Hobbytown has them in stock!

I prefer the EC conectors over Deans as they are easier to separate yet are a positive worry free connection.

Solder the bullets, push into end cap. Done.
Permanent fix for wrong battery connection for parkzone flyers.
Good price as well.

This is just what you need to add to your Thunder Power pro-lite batteries to use in your e-flite plane. (The big Thunder Powers come with just bare wire.)