Polly, it depends on the top and the fleece. I just have to do a touch test. I put a piece of fleece on the top, roughly pen around a few spots so it stays together, and then I feel it. If the seams are too hard through the fleece, I use a batting. But only a very thin one. Some fleece is thick enough to hold up and that's all I use. The weight is great, the quilt is really snuggly and cuddly and wraps around very nicely.
My first "quilt" which was made a good three years before I started to be interested in making good quilts, was for my son who is cold all the time (he's 6'3" and weighs 145 lbs). I used two layers of fleece and just sewed in squares all over to keep the layers together. That is the warmest quilt on earth and will probably still be in existence when some archeologist digs up our long disappeared culture eons from now. He's slept under it every night for ... I think 6 years ... and typically if he's going to be watching a movie he pulls the quilt down and wraps up in it. It gets lots of use. There is no way to put nice points or fussy seam meetings on fleece (at least not for sane people). But it is possible to make simple blocks and so have it be a "real" quilt top all of fleece. I've done it several times and when I take those into the donation offices, the folks always ooooh and ahhhhh over them. It's not easy, but it's worth it sometimes.
Okay, sorry for the treatise on fleece, LOL. I don't even know if I answered your question. But I would definitely back with fleece. It doesn't need close quilting (I have a friend who just ties her fleece backed quilts) and it likes to stick together, so the layers don't move too much once you introduce them to each other. I use it all the time. Buy in big quantities when it's on a good sale at Joann's.
Sunny contemplating my own fleece "blankie"