Most twin engined planes can carry more people than singles but not as much as you'd think. There are a few 4 seat twins although most can carry from 5-6. There are singles that can carry as many people.

Twin engined planes have a pretty high accident rate because they are more demanding to fly. If you lose an engine on take-off in a conventional twin, you're in a world of trouble. In many cases, the safest thing to do is chop throttle and land straight ahead just as you'd do in a single that loses power on takeoff. If you're trying to fly a twin with an engine out and you get too slow, the plane has a tendency to "roll over and play dead." Since you have two engines, you just doubled your chances of losing an engine on takeoff. However, if you lose an engine during cruise or landing, it isn't really a big deal with a twin. You find the nearest airport and land. Losing an engine at any time in a single is a very big deal, especially at night or in bad weather.

Twin engined planes are often more stable than most singles which makes them better for instrument flying. They have more redundancy for vacuum systems and generators which also helps with safety, especially at night or during instrument conditions. There's also more stuff to go wrong, too. The more stuff you have, the greater the chances that something will break. Malfunctions are big distractions and distraction is a cause for many accidents.

There's an old aviation joke that says a "propellor is just a big fan to keep the pilot cool. If you don't believe me, just stop the propellor and watch the pilot sweat!" That's why us single engine pilots are taught to always be on the lookout for an emergency landing site. While engine failures are rare, they can and do happen. It's always best to be prepared.