Do you want Sch 40 or std wall? If it is large diameters, you probably won't find it in seamless and will have to use ERW but in the sizes where seamless isn't commonly available, Sch 40 starts to get really thick walls. Is that needed for chilled water?
You may want two different pipes for the two different systems. Generally chilled water piping is much smaller diameter than fire water mains, though some of the branch piping could be the same size.
Where are you located and what Codes are you building this to (for example, do you have to meet NFPA Code?)
Can you be more specific, it's not the issue about sizes. It's about knowing the exact specs of a carbon steel pipe that one should use for these systems. I am located in middle east.
I would have no hesitation to use ERW instead of seamless pipe in these applications. B31.3 doesn't care which of these two grades you use as long as you apply the seam de-rating factor in the hoop stress calculation.
Some don't like ERW pipe below 2" NPS because they do not believe that adequate weld soundness testing can be properly accomplished at the smaller sizes. But for a Category D service most are not that fussy.
I personally would not buy A53 ERW from China at any size due to wide reports of problems with Chinese origin material of that type.
Either of the materials that you propose are acceptable for this service. Here are a couple of specifications for above grade chilled water pipe systems.