I am planning to climb the Matterhorn (Hörnli) with my wife in September. We have La Sportiva Nepal Evo an La Sportiva Trango Prime boots. Do you think these will work?

These are semi-automatic crampons (no toe welt step in) as opposed to the "automatic" sabretooth pro step in. Automatic crampons work only with boots that have full heel and toe welts and as a result have less play and are more rigid. If you buy a mountaineering boot with full heel and toe welts, like the Scarpa Mont Blanc or the La Sportiva Nepal EVO, you'll have more options. The La Sportiva Trangos have no toe welts but are still great boots by all accounts. I think its really a matter of personal preference. If you are looking to do very steep, technical routes, you may want to lean in the direction of boots with both heel and toe welts along with fully automatic crampons. Otherwise, for most cascade peak summer climbs for example, i think the La sportiva Trango and some semi-auto crampons would be just fine.

Just to answer my own question to help everyone else out, I got the La Sportiva Trango Alps GTX and these crampons were glued to my boot. After you flipped the rear boot welt up you could pick it up and shake it like your life depended on it and it wouldn't budge. Overall these worked great for some pretty gnarly snow climbs

There really is no performance difference in automatic vs clip crampons. automatic's are used primarily by American climbers where as clip (semi auto such as these) are highly favoured by European climbers. That being said, you can't go wrong with either.