That's an easy one
. The Beneteau that are called in Europe Oceanis, are better at a marina or while at anchor, the First are a lot better sailing. They are also more seaworthy with a better overall stability, more rigid (less flex) and with a much better quality equipment (bigger winches, better hardware and so on).
That's why they are a lot more expensive than similar sized Benetaus, even if these have a more comfortable interior (and probably a more expensive one).
With the First options you can specify the boat for cruising (much less expensive) or for several types of racing, from cruising and club racing to only top class racing (and that is really expensive).