Clearly you have no idea of what assisted-GPS really means.
By "assisted", it means the GPS on the device is using nearby network signals (I.e. Cellular), and precise network time for startup (initiation) to locate the area/region you are in, before acquiring an exact pinpoint location from the satellites. Hence the "assistance" speeds up the process of a GPS lock on the satellites and pinpoints your exact location faster.
Billy, while that may be true, it does not mean that the iPad a-GPS will necessarily be faster than an external one. A GPS unit's time to first fix (TTFF) depends on a couple of factors. If all of these factors were the same (i.e., two unit's with the same chips, power sources, etc., were being compared with the exception of assisted vs. non-assisted) then yes, the a-GPS would have a faster TTFF. But not all GPS units are equal - some are most definitely better than the iPad, while others won't be.
Not to mention companies (like apple) know that a-GPS is better, so they put lower power GPS chips in their products to save battery life (since with a strong cell tower signal the standalone GPS capability is effectively irrelevant).
So where people like iPadThai will be better off is in locations where there's no cell tower signal. I don't know what chip is in the iPad but it's worth looking into if you are not sure about which iPad to buy.
A little on a tangent here, but check out the following tables:
http://www.pocketgpsworld.com/ttffcomparisons.php