Deciding on a particular upgrade approach at the right time can improve upgrade performance. Various upgrade options can be chosen depending upon hardware and software requirements. The key benefit of in place upgrade is that it can upgrade various settings and migrate customizations to SharePoint 2010. But with database approach, you will be allowed to attach multiple databases at the same time but each database is unavailable during the upgrade. With parallel upgrade, you can considerable reduce your down time while attaching multiple databases in parallel for upgrading.