Take off the heads or not?

I have been going back and forth on weather or not to take off the heads to correct this valve spring issue that is apparent. I have changed the springs with the heads on the car before so I know that can be done. I could also buy some springs that would give me the pressure that I would need without machining the heads, but I am curious as to what you would do and why? I am sure it is much easier to work on the heads with them off. Let me know what you think?

Thanks,

Hawkxr7