Cross device tracking / Cross domain tracking - same user id?
I am about to start with the tracking types mentioned above.
My question is this: By running both tracking types, is the same user id used in either tracking reports?
Re: Cross device tracking / Cross domain tracking - same user id?
They are similar but independent topics. Cross domain let's you follow the users journey as one session instead of two disconnected sessions. It also preserves the proper attribution (source for first site is google/cpc and remains that on second site instead of showing as a referral) across the sites.
Cross device requires setting a unique user id as a user self-identifies (e.g. log's-in) on each client/device. If you need cross domain (users journey across more than one domain -- not including sub domains) then you need cross domain and cross device will not fill the gaps properly or allow for proper attribution.
Hope that helps.