[greggman]

It really depends on what type of game you're planning to make. Go to any game jam and look at the amazing games prototyped in Unity over a weekend. Compare the html5 games. It's often night and day. The amount of stuff you can get done in an engine you're familiar with so many tools and plugins at your disposal is a huge force multiplier.

Of course do whatever you want. Most of my projects have been HTML5. But at the same time I recognize that free importing of nearly any format of 3d assets into unity and built in animation, collision, physics, ability to edit nearly all parameters at runtime, even code. Is a huge boost once you get used to it.