Check out a bike with a shock fork but one that you can "lock out" like the Giant Roam.....(just using as an example.....all brands have a bike like this).......

Roam 3 (2014) - Bikes | Giant Bicycles | United States

That way, if you get rough road, you can leave the shock on, but if you get a smooth patch & you'd rather go for speed, you can lock the fork & all your pedaling energy will be put to the ground!!!