I prewash and then put the sizing back in. I think the pros outweight the cons. My points almost always line up whether I prewash or not. I think it has more to do with accurate measurement and sewing than anything else. I do not like my fabric shrinking unevenly (I measured. Some can and do) or bleeding all over a project I worked so hard on (I prewash everything once and test again).
I pink the edges and wash, dry, and iron before use. I use Magic Sizing if I think I'll need the extra help. Starch is great for bias.