Choosing a technology... why not Flash?

I want to make a site from scratch, and Im considering to use Flex to make a R.I.A instead of the standard approach (xhtml + css + some ajax).

The kind of site I want to make is something like e-bay, but less complicated.

But.. I know that 95%+ of the sites like that are built in the previous mentioned techs... so, what are the cons and pros if I want to make a 开发者_StackOverflow社区pure Flex site?

Thx.

If you write an entire website in Flash, the entire website lives at one URL. (Short of mucking around with whatever Flash provides to let you offer deeper links.)

Whereas a website written in HTML, unless you go mad with your AJAX, lets people link to the stuff they’re actually interested in, like unicorns:

• http://cgi.ebay.co.uk/DESPICABLE-ME-AGNES-Unicorn-Doll-Plush-Character-Doll-/180602861597?pt=LH_DefaultDomain_0&hash=item2a0cc4f81d#ht_1755wt_907

Or for a non-eBay example, Stack Overflow questions:

• Flash for business web applications - why not?

HTML also has a pretty standard and understood user interface: links, and form controls. (Mainly links.)

Flash doesn't work on iPhone/iPad. End of story.

Other reasons: not a web standard, often quite slow, not good for SEO, etc.

It requires users to have a proprietary plugin which some users don't want and other users can't have (since isn't available for all platforms (iOS being a key example)).

It also has performance and stability issues on some platforms (OS X and Linux being prime candidates).

While some search engines have started to index Flash content (so long as it exposes the information), the results aren't as good as for content rich HTML sites.

You can do that simply using traditional xhtml + css + jQuery (or any JS framework if you want to increase UX). Flex won't do much in your scenario.

In my experience, performance is not a real issue unless you play video - one can write bad programs in JavaScript, too...

Your pros are mostly on the development side: You can have a great looking site quickly, and you can almost completely forget about browser incompatibilites.
You rely on the customers having the plugin installed, though, and you rely on Adobe's technology for development and playing of the content.

If this is not important to you, and you can afford to do without all iPhone and iPad users, accessibility and standards compliance... go for it!

Flex is good if you want to install as an application using Air. ebay actually has a RIA version, or at least they did for a while.

There are several concerns with a Flash site, some of which Adobe has addressed in the last couple of years.

One is accessibility. It is more difficult to make a Flash site accessible to the visually impaired, who use screenreaders.

Related, people like to be able to copy and paste content, as well as print. With standard web pages, the developer need do nothing to support this, it just works from the browser. With Flash, you'll have to take care to make your text content selectable, and I'm not sure a user could ever select a section of text + images. I've never done it, but I can only imagine that implementing printing ability in your Flash site would be nightmarish, at best.

Another is linking and addressability. For most sites, you can copy or at least get a link that you can share or save to get back to where you want to be. With Flash, you usually go to a single address and then the rest of of your experience happens inside the Flash "window" and the browser isn't actually navigating any pages. It is far more difficult to implement this ability in a Flash site.

A Flash site is usually very slow to load, especially the first time, and page load times are immeasurably important to a site's success.

Finally, you've perhaps heard the furor over the last couple of years about different vendors supporting or not supporting Flash in their products/devices. An all-flash site would be completely inaccessible on any iPhone or iPad, for example, which do not support Flash at all. Furthermore, some employers do not allow plugins like Flash to be installed on work machines, so you'd eliminate that portion of possible traffic, as well.

Nobody has yet mentioned Silverlight.?

I mostly agree with Jay's answer concerning accessibility, but as a further note would like to add that development in Flex/Flash vs HTML/CSS/JS could be more costly not only in terms of money but also for maintenance. Many Flex/Flash devs typically charge a higher price and their dev tools, which are necessary for compilation, usually aren't free, compared to HTML/CSS/JS devs, who often use freely available text editors.