There may be reasons not to use either OMA DM or Push install:
Some platforms do no support either method. This applies to Apple and (in part) to Android devices. For more information, see the platform-specific deployment sections later in this guide.
In circumstances that call for a less structured installation (such as during a test phase or when installing during a support incident), you can use ad-hoc installation. See Ad-hoc installation.
For Symbian devices, you can distribute DME on a memory card, which will auto-install DME. See Symbian auto-installation for more information.
For Windows Mobile PocketPC devices, you can distribute DME on a memory card, along with custom configuration. For more information, see WM configuration tool.