I would focus on making it a question of whether the women who are presented as strong are presented in a positive light or a negative light. For example, young Juliet defies her father. Is this a good thing or a bad thing, and why?
One of the most common topics, when discussing the women in Shakespeare's plays, is how strong and outspoken they are.
- the characters who dress as boys, and as such, have the freedom to speak their mind in any company (Rosalind, Viola, and Julia);
- the women who have or desire power (Lady Macbeth, Cleopatra, Regan/Goneril, and Tamora);
- the apparantly demure and unassuming women, who, for love, step out of their expected roles to speak up and/or take brave and decisive action (Desdemona, Cordelia, Hermia, Juliet, and Helena -- All's Well);
- and the women who simply speak their minds, period (Beatrice and Kate).
There are a gamut of strong, capable, smart, outspoken women in his plays. You can see from the above list, that though there are many "strong" women in the plays, they fall into different categories of "strength." I would suggest picking a type of strong female character, finding the characters who demonstrate that sort of strength, as I have done here, and then, in the plays in which each of these women appear, compare them to the other women (Are these women also strong?) and the men in these plays.
The reference link, along with the suggestions I've given above, should help you get started.