But the M110 has some tricks. It is around 15 pounds (versus the Barretts almost 30), can support a silencer, and has some trick optics.
It's also magazine fed but so is the Barrett. Look, I don't really want to compare them though, I want to compare the M110 to other snipers out there. The magazine makes a big difference. More time pulling the trigger than reloading is the main thing. Also, keeping your eyes on the prize is a bonus.
I think I would choose this over many rifles just because of it's accuracy and stealth. 15 pounds and silenced? If you get discovered you can make a run for it and not be too weighed down. But as long as you hole up in a good spot you should be fine.