I'm in the midwest so similar to you, I can go East or West. The best test for ping at the moment is this:

http://www.cloudping.info/

Also, welcome to CoE!

"We're still evaluating hosting companies, and will use real-time performance data during Pre-Alpha and Alpha 1 to determine which host we're going to go with. But virtually all of them are located on the coasts, in Germany, and in Sydney."

It shouldn't be too big of a difference, depending on what you want to do in game -- if you want to do hardcore pvp, I suggest the coast closest to you, with the best ping -- if you want to do minor pvp, and etc. I would suggest finding the group with the best match for you to boost your gameplay experience.

It's always best to find the perfect fit on either server to ensure that you'll be able to have the best game experience.

I'm in the same situation - located right smack in the middle of America, my latency to both coasts is more or less the same. I ended up making my decision after carefully examining the geographical and political landscapes.

I know it's not much help, but I have faith that SBS will find good hosts - so either coast should be ok.

I am in the middle of America as well and i did end up choosing NA-West. I used the ping tool link that Hieronymus had mentioned above after i had selected and it was the lowest for me.

I would look at what groups of people are on each server that you feel you will have the best play experience with to help decide.

I chose NA-W purely due to expected ping time (I'm in Oregon). Using this tool, it shows NA-E as 5x slower for me.

Well, if you're looking at East feel free to check out the kingdoms and communities for that server located here:

https://chroniclesofelyria.com/forum/topic/22216/nae-kingdomduchy-information-welcome