What CPU is better? semprom 145 or athlon x2?

[butteff]

Hello, I have got this cpus:

1.AMD Athlon II X2 270, SocketAM3 OEM [adx270ock23gm]
2. AMD Sempron X1 X145, SocketAM3 OEM [sdx145hbk13gm]

What cpu more better for gentoo compile works?
Where I can find the best make.conf parameters for them?

Thank you

[Tony0945]

Semprons are crippled worse than Athlon II's and single core CPU's are totally obsolete.

EDIT:

Best cpu flag is -march="native". Gcc is well optimized for older CPU's.