What are the differences in a T4 connector and a MC4?

I used Weather Paks in 1990 on the 4 Kyocera 51 watt panels on Quicksilver. Space Shuttle Endeavor/Discovery surplus refit wire from Lockheed. It's like brand new 27-years later. I literally "filled" the connection boxes with dielectric silicone grease then forced grease into all the panel seams. Reminds me - I need to replace the green fishnet coconut deflector on the roof.