This question comes up all the time and seems to bring out the fanatics on both sides.
My experience is that the Memory Map software using the CAA charts is great on the New iPad (there is no iPad 3, there was iPad, iPad 2 and then the New iPad) and with an external Bluetooth GPS receiver, it is fantastic.
I use a GNS5870 MFI receiver, £80 from any good supplier. This lives in my shirt pocket, with the iPad on the passenger seat. When I look at traces done using this, compared with the iPad using inbuilt "gps" to record positions, the differences are enough to make it well worthwhile.
Sample rates are massively better and you have more accurate traces as a result.
I "heard from a bloke in the pub" that during periods of GPS jamming, the iPad & iPhone still know where they are, and the external "proper" GPS devices are screwed. That suggests to me that the iPad's native "assisted gps" is actually just Cellular mast triangulation.