Room tuning

Does corner absorption vary. Lets say between Michael Greens cornertunes and echo busters cornerbuster, BOTH HAVE reflection on one side. does one at shine the other when placed in corners.

Size matters.

Unless you are an acoustic engineer and have performed some precision measurements and know precisely which frequencies you want to absorb then you probably want a broadband absorber. I would not be too concerned. Both your choices will work in a limited fashion. If you treat four corners then you will probably hear some improvement. Broadband absorbing acoustical products rarely outshine each other; they all follow physics so that as you increase size and volume you gain in absorption...similar size and similar volumes treated will not vary in performance dramatically. A small amount of treatment may barely be noticeable. Since both the products you have selected are small then you must be prepared to accept a modest improvement.

Some manufacturers test their products in independent labs. Only these products will allow you to conclusively compare performance. I believe GIK, Realtraps and Auralex have done tests in independent labs. Others may have too (sorry if I missed them).

One thing - treating the corners is likely the best place to get maximum absorption in the bass for the least surface/volume treated - so you are on the right track.