not sure where you are planning on going in the Peak, but the majority of the biggest hills are in the northern part of the region – Dark Peak. none of those are what i would consider massive climbs as the area just doesn’t have the elevation (highest hill is kinder at just over 2000ft). thats not to say they are easy, but they’re not big epics like in the lakes, north wales or scotland. im a overweight, unfit middle aged man who rides a 6inch travel bike round them and cope ok for your normal 15-20 milers.
personally i’d make the decision on what, how long and how you ride. for me, i’d take the plusher suspension as there’s some great relatively technical and rocky descents in dark peak and i like hooning down them
oh, and before someone else steps in, let me take the gold medal for pedantry – it’s the Peak singular, the name deriving from the people who used to live on the tops of the hills, not the peak of the hills themselves, therefore no plural. everydays a school day!