It would be faster and they wouldn't have war with England

While it probably would have avoided war with Britain, it's doubtful that it would have been faster. Schlieffen's plan of attack, and Moltke the Younger's modified version of it, envisioned attacking through Belgium and Luxembourg as it would avoid the French fortress line which guarded the area adjacent to the Franco-German border. When the Germans attacked the Belgian fortress at Liege, it took them well over a week to completely reduce the forts, utilizing 30.5 and 42 cm siege artillery pieces. Reducing the French fortresses would have required similar firepower, but there were too few heavy pieces in the German arsenal at the time that would allow for them to be reduced in a timely fashion, and speed was the key.

Furthermore, the Germans expected the French to mass the bulk of their forces there and attack into Alsace-Lorraine, it being the only area where Germany bordered France and thus could be attacked. Massing the weight of the German Army opposite it would have been a recipe for disaster, as the underlying premise of the Germans' offensive plans was to sweep through lightly defended Luxembourg and Belgium and attack into the rear of the French Armies, across their interior lines of communications, thus avoiding the main concentration of the French Armies further south. Attacking there would only have pitted to very large, well armed forces against one another in the built-up terrain of Lorraine and the Vosges, packed between neutral borders. No flanks to turn, the Germans artillery and numbers are offset by French fortifications and use of railways to ferry reserves, under these circumstances Trench Warfare would have almost certainly become reality much sooner, producing a stalemate Germany could not afford.