Definitely flexi brand
I only use ours in areas that aren't heavily populated and where we won't see many, if any, other dogs or people. I like it because it's really nice to be able to give him a bit more room, and he gets a better workout too because he can go a lot faster, and sometimes I don't want to bring out the 50 foot rope or can't, but the flexi comes in handy for those instances. Although he has a great recall, so I'm not too worried if it broke by accident.
I will say that we have had 2 break on us. They were Flexi brand, but from Walmart if that makes a difference, and the cord kind - not the nylon leash type. Once probably 3 years ago, we saw deer out back and he darted out the door and I was amazed when I was standing there with the top half of the leash, but not the dog. lol. Thank goodness it's a secluded area though, so he chased the deer off and came right back. But he's also 16lbs and pure muscle.
But yeah currently we have the 26ft cord kind that we mainly use for potty breaks when we're at the house, and it's been good to us for over a year now.