I agree with MoverZ, but would like to add the following:
Assuming you're talking about a steam line (hence "water" hammer), you run the risk of slugs regardless of the layout once you go vertical.
You can reduce this problem with steam traps (which should be called water traps), but they might want to replace the first elbow of your loop with a tee, which could make your life harder. Adding the dip or low point is itself the trap.
If your fluid isn't steam, then consideration of whether or not liquids can drop out or vapors flash out are an actual risk factor applies.