Mike posted exactly what I would have said... if skirting busy airspace I would want ADS-B Out for direct visibility to GA and mid-range aircraft (the big guys have TCAS and see your transponder in all situations).

If you are flying near busy airspace are there be cases where post 2020 airspace access will matter to you, like flying over the top of Class C but below 10,000’?

Details always matter. My question would be what Mode S transponder do you have and is your glider type certified or experimental.

If you have a Trig TT22 in an experimental glider then your fully 2020 compliant ADS-B Out install may cost you several hundred dollars for a TN72, pitot switch, and install work, or if that is not the case you could be looking at several thousand and more install hassles.