Bigger horses have a longer stride, so they take up more ground between barrels. And I'm not talking about TB, i'm thinking big QH. If trained right to use their body a big horse can easily turn just as good as a little horse. When I had my 16 hand mare I noticed she didn't turn as tight as my little mare but she turned amazing well for a horse her size. My little mare on the other hand can circle a barrel without another inch of room to spare between it. But she's small, has a long stride for a little horse, but she really has to haul a** between barrels. I have no real opinions on whose better, I see big horses win and sometimes I see some ponies outrunning all the horses. Yes ponies, 13 -14 hh ponies. I do think though that smaller horses make better pole horses.