Motiva or allergen Inspira implants? Anyone use or work with both? Advice?

Having used Allergan implants almost exclusively for 20 years, I now use Motiva for almost every case. They have an internal gel which they call Ergonomix that is extremely soft and a lot of my patients really like this. If you are looking for a firmer result, they do a version of it which they call Progressive Gel. The main difference between the two manufacturers is not so much the gel but the shell and, more specifically, the texturing. I believe that highly textured implants like Allergan's are going to become increasingly unpopular due to potential long-term problems, capsule formation, late seroma and even ALCL in a small number of cases. I have plenty of patients who have Allergan  implants and I would not recommend removing them for the sake of it but, given the choice, I have found Motiva to be an excellent product and I would highly recommned them. (I have no financial interest in the company)

The results that you want to achieve will not be dependant on the type of the implant as all types do have a softer and a firmer option. However, it is important to look at the long term results of any implant and this is only available for the Mentor implant, these results are related mainly to capsular contracture and rupture rate.

The choice of breast implant is primarily to achieve the desired breast shape from the volume of tissue you start with.  The first choice is between round and shaped.  Having chosen the style the implant size is chosen on the width of the base of your breast and the projection required.
Your surgeon has chosen round implants.  These are available in different consistencies from both manufacturers.  In addition, Motiva make a softer implant whose shape is influenced, to some extent, by gravity.
The Allergan implants have a rough surface that adheres to tissues and is less influenced by gravity.  Motiva implants do not adhere and may need better tissue support.  They do though have a very low reported incidence of capsular contraction and the implant shell is less palpable, with palpable folds rarely being a problem.
Your surgeon should be able to advise as to which implant is better for you but, if you are looking for a firm implant that is "form stable", Allergan may be the better option.  The soft touch is slightly firmer than the responsive gel.