I have both and wouldn't get rid of any of them.
My HW100 in .20 is a fantastic rifle, it's accurate, easy to shoot, functional and is well built, I don't worry about it going wrong they're easy to fix.
I have six Rapid's, they're iconic, beautifully engineered, do what it says on the box and easy to work on. All mine are deadly accurate, I did have to tune the barrel on my MK2 but that now shoots any pellet accurately.
For a day out in the field my first choice is the HW100 for the magazine and loading system, this is closely followed by the MFR in .20. For pest control, rats, ferals etc, garden pests the Rapid MK2 in .22 with Falcon Accuracy Plus is my go to gun.
A Rapid shoots just as well as any modern gun if not better, the HW100 just edges it due to the loading/mag but if I kept one gun it'd be a Rapid.