Compare two complexity functions having the same asymptotic complexity
Although, you cannot find the arbitrary constant c from master theorem, you should check using different size inputs which algorithm is faster, because even though both are upper bounded by c*n^2, if we have 4*n^2 and 1/4*n^2, still 1/4*n^2 is 16 times faster !!

A very important point is that your second algorithm seems to use divide and conquer method. This means that maybe it can be parallelized (in order to use more space but less computing time). For example, assuming an ideal choice of pivots, parallel quicksort sorts an array of size n in O(n log n) work in O(log² n) time using O(n) additional space.