Looking on paper at how the dual-core Phenom II was basically the same processor as AMD's current flagship, we expected great things of the X2 550 and ultimately it didn't disappoint.
The newest Athlon II X2 250 on the other had was not quite as impressive. While it proved to be a viable alternative to the Intel Pentium E5400, the $15 price difference compared to the Phenom II X2 550 is too small to justify the savings. It's likely that OEM manufacturers will like the choice of shipping a slower and cheaper processor when producing thousands of computers to sell at retail, but for users looking to build a budget gaming system with every expense spared then the Athlon II X2 250 is the way to go.
The Phenom II X2 550 will be particularly appealing to gamers as it was considerably faster than the Core 2 Duo E7400. It also managed to deliver roughly the same level of gaming performance as the Phenom II X4 910. So the Phenom II X2 550 makes real sense for gamers on a budget as it allows them to spend more money where it's really needed, like on a more powerful GPU, for example.
With the recent arrival of the Radeon HD 4770 at around $100 it would be possible to build the guts (CPU/RAM/GPU/MB) of a gaming system that is capable of running most modern games in all their visual glory for less than $300.
At roughly $100 the Phenom II X2 550 is a steal and its also a cheap way for users to get an AM3 processor.
Another noteworthy aspect of the Phenom II X2 550 and also the Athlon II X2 250 for that matter was their overclocking abilities. Both processors reached a stable overclock of 3.90GHz with relative ease and we are confident given more time both could exceed the 4GHz barrier.
Overall we really liked the Phenom II X2 550 processor as an alternative to the Intel Core 2 Duo series. Then the Athlon II X2 250 does what it needs to in order to compete with similar priced Intel processors, but with such a small price gap, there is no reason why you shouldn't pick the faster Phenom II X2 instead.