Sorry to be ignorant, but recently I've seen posters looking for these qualities and I guess I need clarification. What is a "quick" hind leg? I assume, good hind action and use of hocks? And what is with a "long" front leg? I don't get it. Don't you want long hind legs too? Please, someone educate me! I'm obviously behind the times as usual
Re: Longer front legs - Usually needed in a particular horse because compared to the hind legs, they are short. This can create a downhill balance and not enough expression in front.
Re: Quick hind leg - think snappy and engaged. A horse with a slow hind leg would be one that would get passagey in the trot. The hind leg gets too slow, then therefore gets out behind the horse. Suspension is fine as long as the horse has good engagement and can be quickened behind when asked.
A quick hind leg is one that accelerates. People used to think that what you want is a hind leg that steps further under, but there had been a significant amount of research that states that that is not the case but that good dressage horses have hind legs that accelerate. You want a horse that when he collects he is able to keep the energy going behind. You want activity in all of the work, activity originating from the hind end. Obviously though "quickness" is not the only aspect of a good hind leg.
A long front leg is often desired because it creates the appearance of an uphill horse. Some say the body mass in the front is then placed in a higher position in relation to the hind (carrying )end....in essence actually making the horse uphill vs on the forehand.