My garden is currently in the middle of a wonderful transformation - emerging from the mudbath is a garden I hope to love forever!
I have a long bed against the boundary fence which is planted with fruit trees and a couple of blackcurrant bushes I saved from the old garden. I'll add raspberry canes too. I currently have a pear (no partridge yet), two apples, a cherry and a plum. All relatively new tress between 1.5-2m so no fruiting yet sadly! The bed is up against my raised vegetable bed and is about 12m long and just under a metre wide. I'll need to put something in there otherwise I'll just be weeding and weeding (garden is huge and I won't cope).
I suppose the obvious thing to underplant with would be herbs, but I'm going to have a raised herb garden close to the house so no need. I've put strawberries in the veg garden (old ones I'd saved) and could transplant them, but veggie garden is huge and I need to fill it too!
What would be good to plant and keep the weeds at bay without overwhelming the fruit trees? At this rate I'll be putting bark down as I have no idea!
Conventional garden wisdom is that you shouldn't underplant fruit trees with anything at all, particularly when young because they have to compete for nutrients and water with the things on the soil. (Grass is especially bad).
However, your point about weeding is, I think, a valid one! If the brutal fact of the matter is that the tree either competes with ground cover or with weeds, then ground cover is probably better! I would maybe create a circle that you do keep clear immediately round each trunk (you can mulch this with manure and compost to keep the weeds back and help the tree), and then outside this fill with something like alpine strawberries or wild garlic?
I do like spring bulbs under a tree too, particularly those that come out and are over before the tree really gets going. I have an old Bramley in my garden, with winter aconites, celandines (yes, I know they are a weed but I like them, though I do control them quite vigorously once they are finished!), snowdrops, bluebells, hellebores, pulmonaria - those kind of things.