Unless your software uses CUDA processing rather than OpenCL or Stream, the 5770 will be stronger.
CUDA is nVidia-only, and Stream (less common) is AMD/ATi only, for GPGPU processing that some modeling and rendering software can use.
As far as I know everything I'm working on is using OpenGL so if I choose the 5770 won't be a problem loosing the CUDA
The thing is that I am not choosing which one to buy. I got now the GT440, but I can exchange it for free for the brad new 5770 as the guy who owns it do not need it and will keep the GT 440 just for spare...