Apart from the time and expense (www.lowcostconservatory.co.uk/upvc-conservatories-cost)that goes into building your conservatory there is the task of adding blinds and furniture.
Interior Conservatory Design Ideas
Conservatories & Orangeries Design
In the end it is probably the budget that is the ultimate deciding factor when it comes to the choice of conservatory. See more here: www.orangerycosts.co.uk/modern-contemporary-orangery-home-extensions