1.A is completely / totally / entirely different from B.
2.A and B are different in some/every way / respect / aspect.
3.A and B differ in…
4.A differs from B in…
5.The difference between A and B is/lies in/exists in…
6.Compared with/In contrast to/Unlike A, B…
7.A…， on the other hand,/in contrast,/while/whereas B…
8.While it is generally believed that A …， I believe B…
9.Despite their similarities, A and B are also different.
10.Both A and B … However, A…; on the other hand, B…
11.The most striking difference is that A…， while B…