Hi!
I am currently studying Mechanical Engineering, and there are modules at my university that are for design. In terms of which is better, I can only speak from my experience. I have really enjoyed learning the theory and being able to do design projects. We had to design a pipe climber from scratch in first year which required us to buy our own materials and design and calculate dimensions so it would fit in the diameter of the pipe. We also had to design a device that would lift a car in a pit stop, so that its battery could be removed, and CAD was used for this. As well as this, in our second year we got to use CAD software to design an adjustable camber for an electric go-kart which we got to see to take measurements for and pictures so we could make a design that would work and fit on the vehicle.
As well as that at Coventry there is a formula student team (and at many other universities) that you can be apart of, which would also have designing and hands on experience. As well as this, as a mechanical engineer you can still go into various design roles. I would suggest comparing what both offer in terms of modules and experience and see which one you would enjoy the most/would prefer!
Kind Regards
-Wanita