Everything will work, but to put the windshield on the 15' you will need a different latching post assembly.
Polaris has a kit for this, apprx $25. If you decide to do this, let me know, then I will look up the part number and give it to you. I would also upgrade to the two grommet latching handle.
I'm curious as to why you are looking at purchaseing a 15', as far as the units go, there are some differences, but not enough IMO to change units.