To me it's apples & oranges, really. The Klasse twins ( or brother & sister, lol ) are an acrylic based system which provides exceptional durability as compared to WG. The Klasse SG can be a bit tricky to use, so use the less is more approach when applying. To enhance/maintain the Klasse, use the Sonus Acrylic Glanz & Sonus Acrylic Spritz. Klasse produces a nice glossy finish yet lacks warmth & depth. Some choose to top the Klasse twins with a carnauba for enhanced warmth/depth on darker colors. Ofcourse, a good prep is the key factor that really impacts the final result!
As for WG.....Like some have said, WG produces a warmer, carnauba like appearence. It's super easy to use. For those looking for 3+ month durability from the initial application, WG might disappoint you. However.....Monthly applications of WG ( or even bi-monthly apps. ) maintained with the WG Spray Sealant will keep you & your paint doing the happy dance! I've had terrific results prepping with Optimum Polish, applying a base of Klasse AIO then applying 3 layers of WG on my black truck. I've even used the WG Glaze after the base of AIO. Good stuff.
It all depends on what your goal is. If you're like me, & can't keep your hands off you vehicle for more than 2 weeks at a time ( 1 or 2 washes per week don't count. lol ) go the WG route. If you need longterm durability then go the Klasse route. In closing, we all must admit that what works for some might not work for others. When it comes to detailing products & our opinions it can get into that "subjective" area. Have fun & enjoy the process!!