Smoothness of discrete data

You can use "smoother". And the reason will be following:

You can find the Total Variation (TV) of both the data sets. The variation of B will be much more than A.

The formula of total variation is given by,

$TV(u)=sum_i |u_{i+1}-u_i|$.

The term you're looking for is "variance." When you look at the data, you fit a curve to it. The curve is smooth, but it's the same curve for both data points. The difference is how much the data varies form the curve, usually measured by $frac{1}{n}sum (f(x)-x)^2$ where $f(x)$ is the equation of the curve. The square root of this quantity is known as the "standard deviation"

You can read more here.

It looks like data set A is more smooth than data set B because you can easily see the trend that is there. But, the other thing to know that data set B is [most likely] more well-behaved than data set A because you can get from point to point in set B "freely" without "any traffic" by any points, as compared to set A.

Short answer: Data set A is much more smooth than data set B.