Short answer: A single-band 2 meter radio is plenty of radio for off-road communications.
Long answer: There are so many variations on multi-band radios that some variations may or may not actually be usable by a typical operator with a Technician license. This chart shows the US amateur radio band allocation, permitted users, and transmission types. http://www.arrl.org/files/file/Regulatory/Band Chart/Band Chart.pdf The most common bands on mobile multi-band radios are 2 meter and 70 cm, both of which can be used be used by Technicians using phone (except for 144.00 which is CW only). What you really want in off-road communications is to be able to talk to as many people as possible with as much reliability as possible. Just about (but not every) mobile multi-band radio includes 2 meter. Just about (but not every) handheld transmits on 2 meter. Then there's the digital modes. Digital has amazing functionality, but may not be as useful because not as many people are set up to receive and transmit on digital. If you want to get involved in all the nerdy stuff that encompasses amateur radio, then by all means, get a multi-band radio with digital inputs. Just be sure it can do 2 meter phone, because that's what you'll need to talk to other folks on the trail.