Pot Swapping between Cactus and Euphorbia

Often times I look at a plant and feel that something isn't right.  The plant could use more room, or a plant would look better in a pot currently occupied by another.  Those were the cases for these two plants.

I felt the Euphorbia (I now think this is a trigona, not a canariensis - the parent plant had a much lighter green color and that was throwing me off - but the way this is growing out says trigona) was in need of an up potting to give it some root room for the upcoming growing season.

And here it is in the grow out pot.

I thought the new cactus (perhaps a Mammillaria longimamma) would look better in this pot -