Pretty much what Timop said... the 4670 is acutally a little more powerful in terms of performance, but you gain DX11 and lower power consumption with the 5570.
If you're asking if you should upgrade your 4670 with a 5570 then no, you shouldn't.
No don't replace hd 4670 with hd 5570 as Helltech said...it's better to add little more and to get hd 5670 ..it will be a better replacement for hd 4670 then hd 5570