Where the ring may excel is on a construction site where it may not always be practical to place a flash off camera.The ring flash is less bulky and quick to use - but if it is not your main flash solution but for close-ups you may also check for some third party cheaper options. Savings can go into buying arms/modifiers or the 100L.
Anyway design/architectural subjects may need a different light - depending on the subject (size, shape, material, texture, colors, etc.) - than the flat one from a ring flash (although models which allows to control each side separately are better). The MT-24EX is more versatile for such subjects but also expensive. A flash + arm + light modifier can give the versatility you need to light a subject the way you need.