Just look at the price difference!!!
Well what is the difference other than the price!! They both produce excellent espresso. Both are single boiler machines. Both have a three way solenoid valves, a feature not found on cheaper machines. it releases pressure from the brew water at the end of the extraction drying out the coffee puck making it easier to knockout, more reliable and user friendly. Both are similar in size and in stainless steel, Both have a 58mm commercial size Porto-filters made of chrome-plated brass and large heavyweight group-heads for increased thermal stability. The machines also have identical water capacity, the Classic does allow you to see the water level not available in the Silvia. Boilers; the SIlvia's is 12 ounces, brass, internally heated and 952watts whereas the Classic is 3.5 ounces, aluminum, external heat and 1370watts. The Silvia's boiler is way bigger but comes in direct contact with the water so you need to descale regularly. The Classic is much smaller but has lots more power. So its down to build quality!! which will last the longest?