I think polo is definately a more 'elitist' game if you will, simply because of the huge amounts of money, time, and horses you need to be competitive.
I agree that polocrosse is more approachable because yes, you are only allowed one horse for a game. We play either 6/8 chukkas. You can get away with one horse bacause there are 6 players to a team and 3 players on the field at one time. Each lot of 3 (A 1,2 & 3) play alternate chukkas, so 3/4 a game.
The line of the ball is the same in Polocrosse... Such a major thing for safety! The positions are 1 - Attack, 2 - Midfield, 3 - Defence. 1 is allowed in the opposing teams goal third, and the middle third. 2 is allowed only in the middle third of the field, and 3 is allowed in their own goal third as well as the middle third. You aren't allowed to carry the ball over the thirty yard line (The lines splitting the field into the two goal-scoring areas and the midfield) which means you have to either bounce the ball, or pass to another player.