The two evaluate to the same values.
f = 1/Sqrt[(x - t)*(y - t)]; In[5]:= v1 = Integrate[f, {t, 0, y}, Assumptions -> {0 < y < x}] Out[5]=(* Log[(x + y + 2 Sqrt[x y])/(x - y)] *) In[6]:= v2 = Integrate[f, {t, 0, x}, Assumptions -> {0 < x < y}] Out[6]=(* 2 ArcTanh[Sqrt[x/y]] *) v3 = v2 /. {y -> x, x -> y} g = v1/v3; In[23]:= Table[g /. {x -> 10}, {y, 1, 9, 1}] // N Out[23]=(* {1., 1., 1., 1., 1., 1., 1., 1., 1.} *)