Went for the special as it comes with more ingredients, including more slices of pork. I wouldn't go for the other versions of shiromaru as I feel the serving size at Ippudo is small and those would not be enough for me. I think Ippudo is most suited for those who love tonkatsu broth, but dont want it to be overly rich and creamy (like at Hakata Ikkousha).
However, at $21++, it is rather expensive for a bowl of ramen in Singapore.