why would you use an AAR on a tag?
Because your (original, pre-edit) proposed URL would cause the tag to always go to the Play Store. An AAR is designed to only go to the Play Store if there are no apps on the device that can handle the primary NFC record. See my answer to my own question for more on this.
Your approach of using http://myurl.com/something
should work fine, so long as:
The tag is only supposed to be valid for your app
Nothing else on the device advertises support for that specific host and path prefix