How are you determining that a user is returning to your site?
If you are using something like an authenticated login, with a unique id tied to that user account, that will obviously be more reliable than cookies (which due to things like Safari ITP, and other browser cookie policies making that form of identification less reliable), then yes, your solution is likely better.
Or do you have another way in which you are identifying users?
Or is your Adobe still configured for third party cookies vs first party cookies... if you are using first party, and still have Adobe using third party this will make a huge difference...
I believe that Web SDK uses Server Side Cookies which should be more reliable than even first party cookies, but I haven't started using it yet, so I haven't seen the results...