How hard is this mountain to climb? How do these two peaks compare in difficulty?
Difficulty is such a subjective matter. It depends on the skills of the climber. Something that seems very easy to one person may be nearly impossible to another less experience hiker. When someone talks about how easy or hard something is it is important to consider the differences in ability and experience.
The generally accepted rating system in the climbing community is known as the Yosemite Decimal System (YDS). A rating for a route has four parts: Grade, Class, Snow Steepness, and Length. Snow Steepness and Length are pretty self explanatory so I will focus on Grade and Class in this post. Grade rates the overall difficulty of the entire route while Class rates the hardest part of the route.
Grade is expressed in roman numerals from I to VII. The higher the number the harder the overall route. For example a Grade I is a short day hike up to 3,000 feet of elevation gain and little or no technical climbing. A Grade II is a Day Hike with over 3,000 feet of elevation gained and possibly some technical climbing required. A Grade III is a long day climb with over 6,000 feet gained, a fair amount of technical climbing required or a considerable amount of scrambling possibly with some exposure. A Grade IV is a very long day. It would require a great deal of elevation gain and/or considerable technical climbing and scrambling.
Class is classified by numbers 1 through 5.14. Classes 1 to 4 are rated in whole numbers only. At 5 a decimal place is used to denote each bit of increased difficulty. Class 1 is hiking on a defined trail or or in open country which is as easy as hiking on a trail. Class 2 is hiking off the trail usually requiring some bushwhacking or climbing on a talus slope. In Class 2 you are not yet using your hands. Class 3 is the easiest category of climbing. People generally call Class 3 climbing 'scrambling'. You are now using basic climbing including the use of your hands. Class 4 is for even more climbing. Not only are you using your hands but you may have to search for and select handholds. You are using your upper body to continuing gaining elevation not just your legs. Class 5 is technical climbing. Most people prefer to use a rope as exposure is present. You are not not hiking but definitely climbing.