I have both and here are the differences:
1/ 1020L can playback (but not record) 4 channel tapes, 1011L can only play stereo
2/ 1020L has 3 bias positions, 1011L has 2
3/ 1020L has aluminum knobs, 1011L has black plastic
4/ 1020L has thicker wood veneered side panels, 1011L has thinner vinyl covered panels
5/ 1020L has a cast metal head cover, 1011L is plastic
6/ 1020L has 2 record indicators, 1011L has only 1
7/ 1020L also has a few additional minor cosmetic advantages
As far as performance is concerned, I believe they are pretty much equivalent.