For those who are following this, I have sewn several seams using both methods. I have found ManiacQuilter2 and Dina to be correct. Neither method has resulted in waviness or curving. The only difference I have found is that it is much easier to sew a 3/4" strip onto the top of the sewn strips, rather than on the underneath side. I think I'll stick with sewing top to bottom. Thank you all for the assistance.