You are correct, I didn't include the aliases/roles code as the OP asked about syslogins and sysusers not roles/aliases.
I think both approaches are good.
If the database is restored into a similar system where all the logins exists (think production -> production) ddlgen will work fine. If going to a dissimilar system (think production -> development) where only a few logins exist reconciling the suserid and userid using SQL may be preferred.
Use what works 