fusable fleece i think would be either medium or heavy weight...heat and bond ultraweight is very heavy, and about impossible to sew through...it is used more in non-sewing projects. only the heat and bond lite is really sewable. but they are two very different products (the fleece and the heat and bond) the heat and bond is a paper backed fusable used for applique type projects...draw your design on the paper, fuse to fabric, cut out design, fuse to background...the fusable fleece is used more as an interfacing to add body to purses/totes, projects where you want to press/adhere your (batting) instead of basting. 2 different animals.
if you visit sulky's site they have lots of information on interfacings, fusables, embroidery products ... lots of information.
Pellon probably offers lots of information on products on their site to, i just havent' visited that one.