This horse has the body of a pony but the neck and head of a 16 hh horse... very strange looking to me, almost as if you took two different horses and switched their necks! A horse's body length should be in proportionate 3rds: 1/3 hindquarter, 1/3 barrel, 1/3 neck. This horse is 1/2 neck and 1/2 body. Very odd. I also agree he looks shorter than 14.3. A horse can be a height but proportions can make him look shorter still.
I hope you don't mind, I went and drew some lines on the first picture of your boy to help show you his proportions better. The top line shows how level his back is, the bottom line is how long he is and I chopped him into 3 sections like I said should be proportionate above. There is a smaller "nose line" because I realise he is sticking his nose forward. Even if he had his nose on a vertical, his neck is still 1.5x longer than his barrel or his hindquarters. http://i41.tinypic.com/6tpyxf.jpg
These are not exact, I made this on my laptop without a mouse lol. Just a general reference to help you see where he is at. I hope it helps. :)