I like Gaia for the mapping, especially adding custom maps and layers. What works for you may depend on what maps you prefer.
But I like Motion X for the basic GPS interface when I want to navigate without maps, mark waypoints, etc.
And don't overlook PDF Maps by Avenza. Great for looking at certain maps, like the visitor guides the NPS provides. Or forest service visitor maps, or the CTUC maps. All available for purchase for use with PDF Maps; I haven't seen some of those for Gaia or Motion X.
I also like Trimble's for planning, since it has a nice web interface for marking up a map then synching to the mobile device.
The tougher question is which maps to use for offroading. I prefer the latest USFS topos, since they have more up to date info, esp. on closures and whatnot. Or the CTUC maps, although only for CA, although I think there may be similar ones for other states. And aerial photo overlays are often very helpful offroad.
Rob