As far as the difference in the two turbo's, I tried for years to get the Aerocharger to work for sled applications. I ended up with a shop full of turbo's and parts. My shop looked like a Areocharger warehouse. I never could make the turbo work right or last for a full season. Came to my own conclusion that the self oiling design does not have a way to cool the oil and the oil gets heated up and burns up the bearings. This is just my opinion. Part of what help me come to this conclusion was that after I gave up on the Areocharger I started working with the Garrett and have never had an issue with this turbo. In fairness to Areocharger, I understand they have undergone some ownership changes and possibly improved dramatically from an engineering standpoint.
Another thing I want to point out is you can't compare a Silber kit to a BD kit. They are not the same and you can't get close to the same results with these two kits. One of the reasons the Silber kit is less money is they are using a cheaper Japannese turbo, not a Garratt turbo. They also don't have their own fuel system, they are buying someone elses box to fuel their kits. The options for fueling turbo sleds is fairly limited and even more limited in what works. This is why BD invested money in developing their own fuel system and the reason Boost-It has developed their own system.
Saying you can get the same results with both these kits is like saying you can buy a new car for 15K or you can buy a new car for 25K, they will both get you down the road and back and forth to work, why would anyone spend the extra 10K. The answer is engineering, parts quality, long term durability, tunability, just to mention a few. I have nothing against the Silber kit, it works great for what you pay for, but it's not a BD kit and it's not fair to BD to compare the two IMO. Like most things in this cruel world, you get what you pay for. If you have a budget of 4K to buy a turbo kit Silber is a good choice. If you have the budget to spend 6K on a BD kit you'll get a better kit with better parts and a custom fuel delivery system with more tunability which will provide better on the snow performance if you know how to tune.