The A2's get more than double the fuel economy. This is big if you really plan to stack on the mileage. The 8.3 is nearly half the size with a turbo, but same total hp potential (10hp higher if I remember correctly). The 250's have way more low end, the 8.3's have more top end (power), and the 8.3 is capable of higher top speed (RPM), as the engine is rated up to 3400rpm in its marine application. Tires are rated to 50mph or whatever, but the newer ones are rated at a higher speed, though they are slightly smaller. I'd consider all of this if buying a truck to put a lot of miles on. The money you save over buying an A2 may quickly be surpassed in fuel costs if you are really driving it a lot. 4mpg vs 10mpg. Both good engines. The 8.3 is supposedly a 600,000 mile engine, or so they say.