Our first 5th wheel hitch was a Reese 14K single pivot. The single pivot hitch actually has one advantage - the 5th wheel benefits from the roll stiffness of the tow vehicle. In other words, the truck's rear anti-roll bar provides some roll resistance for the 5th wheel.
The biggest problem with the single pivot hitch is in hitching or unhitching when on uneven ground. If the truck and 5th wheel are on different horizontal planes, the hitch will "get in a bind" and can be difficult to engage or release.
Now having had both, I'd spend the $100 and go with the double pivot hitch, but that's just my personal opinion.
Rusty (posting under the better half's logon)
2000 - Texas Boomers Wagonmaster - 2016
2004 & 2008 iRV2 National Rally Wagonmaster
Texas and Boomers - we just naturally go together