Cost

• Compared to the X1050, the Radeon 9550 is an older card, so you'll get lower performance. However, you'll also save when it comes to price--through most third-party vendors, the Radeon 9550 is cheaper.
  
  

Chipset

• While the 9550 is based off of ATI's RV350 chipset, the X1050 features the RV370 chipset and touts a Rialto bridge chip. In terms of sheer performance, the RV370 is faster because it's newer. The X1050 also natively comes in a PCI-X form factor--the Rialto chip allows for the X1050's AGP-based version to function.
  
  

Clockspeed

• The 9550's GPU operates at a modest 250 Mhz, while its memory clocks in at 200 Mhz. In contrast, the X1050 runs at 400 Mhz and 333 Mhz for core and memory, respectively. Graphics cards processing works similarly to a computer's CPU--the faster a graphics card runs, the better the card performs.
  
  

DirectX And OpenGL

• Both cards feature DirectX 9 and OpenGL 2.0 support. By this standard, neither card is especially up-to-date--Microsoft is currently on DirectX 11--but if you don't plan on playing many newer games, you likely won't notice the difference.
  
  

Form Factor

• Before choosing between the 9550 and the X1050, make sure your motherboard can support the card. While the 9550 only comes in AGP, the X1050 features both an AGP and PCI-X based verson. If your motherboard doesn't have a PCI-X slot you won't be able to use the PCI-X based card.