Cu totul ca in css width are aceiasi valoare.

Solutia este simpla de bagat la ambele in css:

-ms-box-sizing:content-box;
-moz-box-sizing:content-box;
-webkit-box-sizing:content-box;
box-sizing:content-box;
border: none;

De aici m-am inspirat: http://stackoverflow.com/questions/4073768/how-to-get-equal-width-of-input-and-select-fields