Yes, Deere John, 12 in/lb equals 1 ft/lb of torque. Rubicon's answer about BHP is right on. BHP or usable horse power is the main number to use to compare a saw's power.
But because chain saws don't have variable ratio transmissions like trucks, horsepower isn't the only factor affecting cutting speed. This makes Huskyman's point about RPM listing is very important.
Husqvarna model 55 and 346XP are both rated at 3.4 HP. Many chain saws are designed to make maximum horse power at 9000 RPM. So, while cutting a large log at near 9000 RPM, the 55 and 346XP will cut at the same speed.
The rated maximum RPM for the 55 is 12,500 RPM. However, the rated maximum RPM for the 346XP is 14,700 RPM. This means that on a small log that requires less than maximum torque, the 346XP will have a higher chain speed and thus cut faster than the 55 even though they have the same HP.
For this reason, it doesn't make sense to put a long bar on a high speed saw: - either you are trying to cut smaller wood faster, or you are making a compromise, trying to do two things at once.
Different chains sizes, (91, .325, 3/8) require different amounts of torque to cut at the same speed and also effect how fast a saw can cut at its rated RPM.