I didn't follow your provided links, but I'd expect the Mag .61 to put out a lot more power than the OS .46, that's for sure. The Mag .61 is also going to be a lot heavier, it simply is a bigger engine.

The Magnum line, in general, is one of the less expensive lines of engines, and OS is, in general, one of the most expenseive for engines in the same size/power class. So comparing by price isn't really the way to go. Instead, you want to pick an engine based on what size/power/weight you want, and then look at the various options and the price compared to what you get for the money.

Obviously, OS isn't out of business, so a lot of folks think that an OS engine that is the same size and power output of a Magnum, but costs a lot more has something else to recommend it.

many people think OS is a higher quality product than Magnum (and some other brands). The quality control should be better, the engine should start better and last longer and be easier to run, and therefore worth the extra money, even if it puts out the same power.

Weither the engine actually is or isn't better, or actually worth the extra cash is a topic of debate . You'll find guys who will only buy OS engines, and guys who think OS engines are overpriced and that some other brand is just as good and less expenseive.