Why build a web game using Unity, rather than Flash, Shockwave, or some other web player plug-in?

As a developer, I'm already sold on the benefits of Unity 3D. However many clients have yet to be convinced that they should use any plugin other than flash for web games and other interactive content. So what I'd like are some killer reasons, ideally backed up with evidence, statisics or other data that would convince a client to try using Unity 3D for their web content. The kind of content I'm talking about would be typical high-end highly interactive web content such as product demonstrations, 3D advergames, TV programme tie-ins, etc.

For this question, answers relating to benefits to the developer (such as "being able to use C#", or "supports shader programming") are not relevant.

This is about benefits that the client or end-user would be able to appreciate when comparing their experience of a Unity webplayer game with webplayer games in other platforms (such as Flash or Shockwave). I have gathered some thoughts together on this already so I'm going to post them as an answer, but I'd love to hear additional answers which cover topics that I may have missed.

Visual 3D quality

Unity wins hands-down on 3D visual quality over both Flash and Shockwave, offering console-like 3D graphics in web browser. While flash and shockwave both have 3d capabilities to varying degrees, neither offer modern hardware-accelerated 3d graphics, making use of modern shaders, visual effects and rendering speed.

Engine Performance

The Unity web player executes code many times faster than Flash or Shockwave (the Unity website says, "20x faster than Flash or Director based JavaScript"), and combined with the built-in "Ageia PhysX" physics engine means that it's able to execute realistic 3D physics, complex AI and other intensive gameplay-specific code very smoothly.

Plug-in install process

Unity has a very quick and simple install process, with no additional payloads (unlike Flash's "McAfee security scan" or Shockwave's "Norton security scan" - or any other "helpful" toolbars, etc). In addition, it can be installed on windows without requiring an administrator account!

Plug-in penetration

A common criticism of Unity as a choice of web plug-in is that it has a low level of penetration - Flash, and even Shockwave, have much higher levels of plug-in penetration than Unity. However, plugin penetration levels matter less than they used to because most home users now have broadband - which makes the actual download time negligable. There are statistics (from both Unity and 3rd parties) which show a respectable 50-60% conversion rate - the ratio of "non-unity-installed" users hitting Unity content for the first time, compared with the amount who make it through and view the content.

This decision that users make to install the plugin can be sweetened by presenting the user with a clear idea of the benefits of installing the plug-in. This is typically done by embedding a video of the content on the page which a user sees if they do not have the plug-in. Joachim Ante, Unity's CTO, stated that "Good content, that people actually want to play, that has a very good presentation for the plugin installation process can do very well. Some customers told us about success stories of 70-75%"

Though not an argument for using Unity per se, mentioning well-known household-name brands that use Unity can still help to convince, using the logic that these well-respected brands wouldn't be using Unity unless there was a very good reason.

The short answer:

Unity offers a complete and fast 3D engine with a wide range of compatible platforms, growing every year!

Like Duck, I'm a big fan of unity but need a similar argument for using it. Having thought a little about it what my response might be there are 2 key areas that I need answers to:

For clients of the type mentioned above there are typically 3 :

1) What am I getting? Marketing clients typically are given a pot of money to spend promoting something. Getting more, or even the same, for less money is a very key benefit.

2) How quickly can I get it? As above, marketing clients typically have a very limited schedule to get a product promoted. Being able to get something done quicker is another key benefit.

3) How effective will it be? If the technology is adopted, with all its potential quality, cost and time saving benefits, how many people are ultimately going to interact with it?

The data needed to form a good argument could be gained from answering the following 2 questions:

1) If we where to, very hypothetically, build a game in both Unity3d and Flash, where would the big differences be in effort and schedule.

2) Has anyone got any case studies discussing techniques used to promote a Unity3d game/experience (as with the video idea mentioned above) that resulted in plugin installation, some solid numbers around that would also be invaluable.

Hey Duck, This isn't an answer to the question so much as a re-visitation of it as I think the web landscape has changed dramatically in the 14 odd months since you first asked. If someone would like to modify the original question with some of these points, feel free.

What exactly is the adoption rate of the Unity Web Player these days? Does anyone believe it will grow in light of the growing anti-plugin zeitgeist among the web community that's begun bleeding into the public consciousness?

Is Unity's web player permenantly relegated to being an also-ran in light of the fact that you can use the tool to create mobile native apps (thereby getting the content onto the currently coveted mobile space), but are not likely to ever get a unity web player running in Safari on iOS?

You should definitely use Flash. 10.1 is gpu accelerated and can even port u3d files.