There are two advantages to the Pathway.
First, it has a larger dish inside than the Tailgater does so will have a little higher signal strength (which might make a difference during rain or partial tree cover, otherwise, it's a "don't-care".)
Secondly, it supports using two receivers for viewing two different channels, assuming you buy two receivers. (This is a nice feature if you have (or can add) the wiring in your RV to support a second receiver.) Note that the second receiver has to be watching a channel that is received on the same of the three satellites as the other receiver.
As for price, CW is selling the Tailgater and receiver for $439 so that looks to me to be $61 cheaper than the Pathway (which may come down once CW starts selling it).