What is better a Chevy 350 or a ford 351?

The simple truth is, there isn't much difference.

Ford and GM have been trading engineers back and forth for so long that there ARE no real differences between the two.

Both are Excellent engines. That is a matter of opinion. I am a sm. block lover, so you know what I think. but don't under estimate the 351. I had a 1970 ,351 Cleveland, and it was a great engine. I ran, and beat many sm. block Chevys with it. (but I like sm. block Chevys.) The only thing against the 351 is the larger main bearing size . While this is good for a low speed engine at higher engine speeds the outside of bearing surface is increased to point of failure due to mass and speed of surface . But they have done some work on that to help oiling and strength so it's all in what you like .