Well, the average banjo has an 11-inch head. If there is a music shop near you or if you know someone with a banjo, you can make a dimensional estimate of what size the Duke10 is by measuring where a 17-inch scale (nut to bridge) would be by measuring from the bridge to wherever on the fretboard 17 inches is - that's the length not counting headstock, Weightwise, the Duke10 is a feather compared to any banjo I've ever held (especially my Deering!). The difference between an 11-inch head to a 10-inch is not as dramatic as going from 10 to 8, and can give a general impression of how the 10-inch matches to the person.
Have had both the Sidekick and the Duke10 simultaneously. Soundwise, the Duke10 is more robust than the Sidekick, but the Sidekuck is no slouch. Weightwise they feel identical. If one keeps the head properly tightened and uses decent strings the Sidekick is a gem.
The first-generation Sidekick did not have a built-in pickup. That does make a money difference and the pickup's value depends on the player's use of the instrument.