The standard cellular antenna connected to the VT unit usually works fine under the van's bench seat, but if you live in a remote area or want the best chance for connectivity, a 9' wired antenna that you can mount in a part of the van with more exposure to the sky may be preferred.
The standard GPS antenna is on a 9' wire, so an antenna wire will have to be run regardless. This upgrade is a combination GPS + cellular antenna, so running the extra cable isn't extra work compared to a standard installation. If you need more than 9' you can order an extension here.
If you don't want to upgrade now, you can purchase an LTE antenna at a later time from places like data alliance. Be sure to choose "SMA," not "TNC" or "RP-SMA" for the connector type.