How do you rate "Play drive" in horses?

I have a mixed experience with horses with a big play drive. The ones I have had with a big play drive are the ones running around in pasture, pushing the other horses around for no apparent reason, biting branches on the tree and pulling them over, laying under the fence to get at fresh mowed grass, standing in the water tank etc.... They also tend to try a lot of unusual things under saddle and can be very resourceful there too and not always in a good way. They are determined and don't give up easily if they don't like a corner or refuse a certain lead that day. And, they aren't easy to correct because they are often really enthusiastic about their ideas.

In general though I like it because the horse is just more engaged and "on" than the quiet more introspective type of horse. Usually this high play drive horse is a sensitive type of horse who easily tunes into the environment to be able to find things to play around with. They are the first to hear turkeys in the bush, be worried that the horses in front are going faster, or be at the gate to be caught. Very aware of placement, space, and timing to be able to dart in, grab something, and goof off. They are confident enough to try all manner of gymnastics, arial maneuvers, cross cantering in mid-air while you only asked for simple lead change kind of antics. I swear they do these things not to be mean but "just because I can". I swear some of the high play drive horses I have are laughing a bunch of the time, but just don't have the vocal cords to laugh. I see the sparkle in their eyes and feel the spring in their feet. They often do not "mature" the same way other horses do and forever act like a four year old.

It's generally fun to be around except when they are playing with me and I want them to be business like. The good things about these high drive horses are, energy, enthusiasm, a lot of try, always listening, often stronger and quicker than other horses. The bad things are they chase other horses a lot, instigate fights/commotion in the pasture, often too tuned in to things outside of the arena (there could be fun things out there too you know), can be tough for a newbie to handle, and they just don't let reprimands phase them very much making them a bit of a bugger to train through an issue. While the other horses are standing there snoozing in the sun, they are goofing off, running in circles pulling a branch with their teeth, using the water trough as a pedestal and others.

It's very cute and endearing until they bust a window, stick their foot somewhere it shouldn't go or rest their head on your shoulder and actually rest it there with all that weight.

It's good. Playfulness is a sign of intelligence in animals. I suppose when looking for a new horse, you'd have to either observe the horse for some time or ask the current owners about playful behavior.