Slave Play, hands down.
I found the Inheritance to be trite, over-indulgent, mostly over- and poorly- acted, way too long and drawn out, and really surface level when it thinks it's delving deep into something special. Direction is spectacular and the final scene of Part 1 is great - those are the only good things I can say.
Slave Play, on the other hand, is deep and meaningful, brilliantly written, has several fantastic performances, and breezes by.
I don't know anything about you, your background or what you're in the mood for but for what it's worth I am a cis-gendered, white, gay male.