The weight you lift for a front squat should be similar to what you use for a back squat. So if you are unable to go as heavy, it may be a flexibility limitation - you might need to stretch out your ankles more or develop your core. Alternatively, it could just be that you need more practice for your front squat!
Front squats are different to back squats because you should be in a more upright position and there is less weight on your lower back. We give you both for the reason that you work in slightly different ways - so don't leave them out!