If you are used to a Pyrenees mix, I wonder if a purebred lab or golden will seem super high energy? Pyrenees are generally very calm and laid back-not a breed I would consider high energy; however, with lab or herding breeds in the mix, that might amp up their activity level a bit. Just a thought.
As far as labs vs. goldens, I can only speak from my experiences with them as a groomer, as a golden owner, and as someone who knows lots of purebred labs and lab mixes (however, I have never actually seen or met a well bred lab, so bear in mind that these things I'm stating about labs are all about the ones from bad breeders-I imagine a well bred lab would be much different!). In my grooming experience, labs are far more likely to have some form of aggression-fear, dog on dog, even towards people. I actually use as much caution with an unfamiliar lab as I would with a breed like a pit that is well known to have aggression in many individuals in the breed! However, having said that, I don't believe I've EVER seen or groomed a lab that actually came from a good breeder. But the fact is, my own golden is the only golden I've ever groomed that comes from a great breeder; and I've only groomed two goldens out of dozens that had any forms of aggression. So it would seem that even from bad breeders, goldens are still tending to have better temperaments. As far as training, my goldens and any golden I've ever worked with is like the easiest thing in the world to train-they are incredibly smart and are deeply loyal and want to please you! Any labs I've ever worked with are a bit more stubborn and just don't seem quite as smart or loyal as goldens (not that they aren't smart, I just think goldens are even smarter!). Actually, the most stubborn dog I ever worked with was a 6-7 month old lab puppy-I was helping his young owner teach him to sit-that dog locked his back legs and flat out refused to sit, even while pushing firmly on his rump and offering treats! As far as activity, both are high energy and will need adequate exercise in order to avoid destructive behavior-and that is more than just a leash walk around the block, lots of off leash running time, playing fetch, long hikes, my golden even goes on 10-15 mile or more horse rides with us. Labs I've worked with seem more hyper and seem to have less of an off switch (unless they are morbidly obese-which is also a tendency I see in ALL dog breeds-but you don't want to overfeed your dog just to make him "calm". And while we're on the subject, I feel like conformation labs are shown obese which is terrible for teaching the public what a lab should look like-now everybody thinks their obese lab is how they are supposed to look.) My goldens have been go all day full speed ahead while outside, and then total couch potatoes/cuddle bugs inside. Some of the more poorly bred goldens I've groomed are more hyper to. Both breeds shed a lot, but labs shed so much they almost make goldens look like they don't shed, lol. Both breeds have health issues so you'll want to find a breeder who is doing all the recommended clearances. Basically, in my experience, if you want a lab or a golden that will be the dog with the temperament, train-ability, looks, etc that they are supposed to have, make sure you find a REPUTABLE breeder! Obviously, I'm prejudiced toward goldens
but whatever breed you get, you will be SO GLAD you got one from a reputable breeder-there is a very noticeable difference between well-bred and poorly bred (or even just so-so bred).