Rawhide adds mass. So if two bows are equal in all things (wood, design, string follow, tiller profile, etc) then adding rawhide to one of them would add more mass and slow down the limbs somewhat.
Sinew also adds mass. A sinewed ELB would have a lot of cast-robbing mass, but put sinew on short bow and things get better.
But it's all about choosing a design that compliments your materials. There isn’t simple answer since so much depends on the design of the bow itself.