Short answer is to buy the one with the Bowens mount.

Look at Westcott and see which speedrings they offer for the modifiers you want. You'll probably find that they offer Bowens mount (which is very common) along with several others. Godox mount is really only supported by Godox (that I've seen) and so far they don't seem to have a very robust line-up of modifiers. Most large modifiers are built around a "speedring" which is the part of the modifier that connects to the lighting mount. This speedring design lets a company like Westcott make the same product available to users of many different lighting systems and all Westcott have to do is change which speedring they ship with the modifier. This also means if you want to move to a different lighting manufacturer in the future, one that uses a different mount like Profoto for instance, you might still be able to use your existing light modifiers by buying the correct speed rings and swapping out the Bowens mount speedrings.