Allomancy might have more immediate results and doesn't require you to be weak for an amount of time, but at the same time, when would you realistically need anything more than pewter, tin, and maybe emotional metals? Most metals are either harder and more expensive to get, or just wouldn't be practical for anyone without some form of ultimate motive with the powers. The same could be said for feruchemy, I probably would never use iron, and probably not tin either. But I would use copper like there's no tomorrow, and I would use things like pewter and gold for short bursts of strength and healing that I might need every once and awhile. While allomancy is cooler and has better results, in our day in age, it seems more novelty than practical. Especially financially. Even if you might have to look like a scene kid with all the rings and other metal on your body..