I'd say an even mix of both, mainly weeds during summer. They're much better for your tort. When I went to school I fed my girl in the morning, now she wakes me up around ten to eat. They can be set on whatever schedule you set but I'd recommend morning/afternoon so the food doesn't sit in their stomach all night.
I'd say go for weeds as much as you can. Try to find some of the original plants of all those salads. For example common chicory (Cichorium intybus) is the wild form of chicory (Cichorium endivia), Radicchio and other salads. Those wild forms have often better nutritional values for the tortoises and they are what the tortoise would encounter in the wild.
That said I do not think it is wrong to supplement a bit with dark leafy greens and such, but if you have a big variety of weeds available I'd go with those.