What age do you guys recommend?

1-2 years

That's what I've heard. I guess my question is more about what is the advantage of disadvantage of getting it done early (closer to one year) versus waiting until closer to two years?

What I've learned from talking with veterinarians is that a pup isn't fully mature, especially the larger breeds, and their growth plates fully closed, etc. until around two years. So, I would rather err on the side of caution and wait longer.

Daughter just got her ECS neutered last week at a year and a half. He seems to be handling it well and the vet, who is on the conservative side, was ok with doing it at that age.

I don't neuter mine anymore but in my recent dog searches several of the breeders have it in their contracts as part of their health guarantees (those that give them) to wait 2 years if you are going to have it done. I don't neuter anymore so I'm fine with that.

Do you know why they say to wait until 2yo?

So their hormones can do their work with maturing their bodies to adult levels. Things like bone growth, immune system, muscle development etc. Hormonal system is intimately linked with the nervous system in directing all body functions like in humans. With female dogs some say wait until after their first menstrual cycle, meaning their hormones are at sufficient levels to be functioning as an adult. The only problem with that is some female dogs may take 6 months or so for their first some may be a year or 2. Hence the 2 years as a general time male or female. This does vary by breed and the size of the dog.

I would add considering the health of the dog is obviously important but also your family situation and presence and gender of other dogs, living situation etc. So sometimes it just makes sense for all concerned to spay or neuter the dog earlier rather than later.

^^^^^^ this in spades^^^^^

My neighbor up the street neutered her Vizla puppy before 1 year old and it grew into one leggy clumsy looking dog which now has serious orthopedic and health issues.

As a veterinarian and bird dog owner I would recommend waiting until dog reaches "fully grown" for that breed. In most cases this is near two years old. Hormones produced by testes (not just testosterone) drive development of muscles and nervous system. After that point it is pretty safe to have your dog neutered and will not affect structure of the dog if done right.

My ex-wife threw a fit when our female lab had her first cycle and was "spotting" on the carpet, so she was neutered. At age, three or four (can't remember exactly, its been a few years) she tore her MCL. We were referred to a veterinarian that did the surgery and talked about what he called and "epidemic" of knee issues in larger breed dogs that had been spayed or neutered too early in life and not allowed to fully grow.
I know this has been stated above, just thought I would give a real life example of why you should wait.

It looks like the consensus is to wait. Thanks.