On a Dx sensor, why not go for one of the 50mm lenses? Taking the crop factor into account they'll give you the AoV of a 75mm lens on 35mm. The Tamron is a great lens for portraits on 35mm (or FF) but can be a bit long for indoor portraits on a Dx sensor. It (the 90) is a great performer for macro as well as portraits which may tip the scales in its favour if you have the space to use it for portraits.