Thanks for everyone's input so far. To clarify, I do know that I want to get a MQM kicker to push me from Silver to Gold. Lounge access is my primary reason for wanting to either buy the membership for $400 or apply for the AMEX reserve.

Free SDC is nice, but 95% of my travel is business related and I would expense any change fees

I typically only fly Delta and if not, Southwest. Accessing non-Delta lounges would probably not be a benefit that I would use.

The extra roughly 10K MQM for the $50 difference in the AMEX vs. Sky Club Membership is enticing given that I would rollover almost that whole amount.

The free companion ticket would also come in handy as I would use that for my wife once a year to go on a trip with me.