That one in the link is just a little different, I had to get it in wide, and this one here is not wide. Abetta also usually runs a little narrow, so I really think you would like this saddle. Good quality for a GREAT price! You wont find a better saddle for that price. Unless its used, or old.
If you are unaware if your horse needs a full or semi, then get someone to help you who does. Usually someone at your local saddle/tack shop should know how to properly fit a saddle. Otherwise, see if your trainer, barn owner or someone of that sort knows. If you are trying to purchase a new saddle, you should probably know what to look for and what fits your horse best.
Semi QH are generally on the "narrow" side of trees, but to get the correct fit, you'll need to get measurements. Most saddle will have "gullet width" in inches, and I THINK that's where the saddle should be on the widest part of the withers. You can measure your horse by bending a wire coat hanger over his withers to get the shape.