You can now choose to log in to bitwarden.com or bitwarden.eu in their app is there any difference why would one choose the other over another?
Edit: It looks like bitwarden.eu is better because it’s hosted in the EU, while bitwarden.com is hosted in the US.
Thats the login, but where resides the database?
EU has stronger data protection in general of course, but is there actually a meaningful difference here? If Bitwarden does its job, nobody should be able to access the data anyway. For new users choosing .eu wouldn’t hurt, but I don’t see that many actual benefits that might justify switching a .com account over.
Bitwarden data regions are separate, and your account or organization only exists in the region where it was first created.
And for anyone with an existing account that want to switch, do note that it’s a bit of process to migrate with no real security gain.
A complete manual migration involves creating a new account in the preferred region and beginning the new organization creation process. Once the new organization is configured, re-invite users, and then export vault data from your old organization and import into the new one. Users will need to manually export/import their individual vaults.
Complimentary families plan for enterprise employees must be based in the same region as the sponsoring plan. If your enterprise plan migrates to another region, it will end your families plan sponsorship. You will need to migrate your families plan and then sponsor the new plan following the steps in the Redeem Families Sponsorship article.
My understanding is that switching to EU server entails exporting one’s vault, creating new account and migrating your subscription to a new region by contacting support.
you beat me to it
If you’re registering for a new account, I would just choose whichever one corresponds to where you live. If you live in the US, your data is probably subject to US law even if you host it in the EU, so if you use the EU server you’re potentially exposing yourself to the laws of two jurisdictions instead of just your own. The reverse would be true for EU users.
Even besides the potential jurisdiction considerations, choosing the one closest to you will perform better.
Don’t overcomplicate things 
If you don’t live in either the EU or US, or if you already have an account, I agree with @iustitia that there’s not really a reason to prefer one over the other.
Adding to that, the EU is not a jurisdiction but dozens of them. Each country has its own implementation of GDPR with slight differences that can prove meaningful in some cases plus its own assortment of complementary privacy and data storage/retention legislation.
Having said that, I would agree with the advice when it comes to a business, but for individuals its dubious. Depends on whether you look at it from the perspecting of you potentially going after bitwarden or an affiliated company, in a legal sense, or from the perspective of your government trying to get data on you from bitwarden