Since you'd have to purchase one of these for each channel you want on the 2nd antenna, I don't see that as a 'realistic' option.. maybe 1 or 2 stations, but not all the stations from another city. For example, I use one of my antennas for my local stations (Harrisburg/Lancaster, PA) with a pre-amp and then another antenna for the Phily stations (5 or 6 stations in all).
How are you doing this now? If it works, then you don't need one. The join-tennas are particularly useful when trying to avoid multipath. In my setup, my CBS and FOX stations are to the NE at about 55 miles. However, the ABC station is on a mountain about 5 miles to my west.
Since my antenna is pointed NE, I tend to get some multipath from the other mountains in the area. Getting 2 antennas and using the join-tenna eliminates the multipath problem from the ABC station.